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About Google Book Search Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web at|http: //books .google .com/I PRACHCAL COAL MINING GRIFFIN'S GEOLOGICAL, PROSPECTING, MINING, AND METALLURGICAL PUBLICATIONS. Geology, StratlgFaphleal, „ Practieal Aids, . „ Open Air Studies, Prospecting for Minerals, Food Supply, • New Lands, . Building Construction, Ore and Stone Mining, . Elements of Mining, . Coal Mining, ... Practical Coal Mining, Elementary „ Electrical „ Mine Surveying, Mine Air, Investigation of. Mining Law, Blasting and Explosives, Testing Explosives, . Mine Accounts, . Mining Engineers' Pkt-Bk., Petroleum, .... A Handbook on Petroleumi OUFuel, .... Metallurgical Analysis, . Microscopic Analysis, Metallurgy (General), . „ (Elementary), Getting Gold, . Gold Seeking in South AMca, Cyanide Process, . C^aniding, Electric Smelting, . Electro-Metallurgy, Assaying, Metallurgical Analysis, Metallurgy (Introduction to), Gold, Metallurgy of. Lead and Silver, Iron. Steel, Iron-Founding, . Goldsmith and Jeweller*s Art, Precious Stones, . if tt »» B. Ethbkidob, Pbof. Gbenyillb Colb, t$ It 84b. . lOs. 6d. . 88. 6d. S. Hebbbbt Oox, ... 68. BoBT. Bbuob, . . 48. 6d. H. B. Mill, D.Sa, ... Ss. Pbof. Jambs Lvon, In PreparaHon Sib 0. Lb Nbvb Foster, 84b. I, M net 7b. 6d. H. W. HuoHBS, , net 248. G. L. Ebbb, . . 88. 6d. net 78. 6d. 78. 6d. net 6a, In Preparation . 10a. 6d. net 68. . IOb. 6d. . 88. 6d. II D. BUBKB, Bennbtt H. Bbouoh, FOSTBB AND HaLDANB, 0. J. Alfobd, . 0. GnmcAKM, BlOHBL AND LaBSBN, Pbof. J, O. Lawn, . E. B. Field, . Sib Bovbbton Bedwood, In I'reparcUion Thoicson and Bedwood, netSs,6d. SiDNBT H. NOBTH, . : net 5b. Maoleod and Walkbb, . net 12b, 6d. F. Osmond and J. E. Stead, net 78. 6d. Phillips and Bauerman, Pbof. Humboldt Sexton, J. 0. F. Johnson, . Theo. Kassneb, Jambs Pabk, . Julian and Smabt, Bobohbbs and McMillan, W. O. McMillan, . J. J. AND 0. BbBINGBB, J. J. MOBOAN, F.G.S., SiB W. Bobbbts-Attbtbn, T. EiRKE Boss, D.So., H. F. Collins. 2 vols., Thos. Turner, F. W, Harbord, Pbof. Turner, Thos. B. Wioley, Dr Max Bauek, 868. 6s. 88. 6d. 48. 6d. 78. 6d. fie^21s. net 21b, IOb. 6d. 10s. 6d. 48. 188. 21s. each 168. 168. 258. 8s. 6d. 88. 6d. net 428. LONDON: CHARLES GRIFFIN A CO., LIMITED, EXETER STREET. STRAND. PRACTICAL COAL MINING : A MANUAL FOR MANAGERS, UNDER MANAGERS, COLLIERY ENGINEERS, AND OTHERS. BT GEORGE L. KERR, M.E., M. Inst. Min. E., OXBTIFIOATXD COLLIERY IfANAGKli. WITH NUMEROUS PROBLE&iS ARISING FROM COLLIERY WORK AND 523 f fdured an& Biagramd. FOURTH EDITION, ENTIRELY REVISED, RESET THROUQHOUT, AND ENLARGED. LONDON : CHABLES GRIFFIN & COMPANY, LIMITED. EXETER STREET, STRAND. 1905. [AU Rights Reserved.] JVl '>! 1909 Uo^lP^^^ N\V_X PREFACE TO THE FIRST EDITION. Not many yean ago the works on Goal-Mining were few, and in most instanoes so expensive as to be beyond the reach of the ordinary student or practical miner. This state of afi&drs has been to a large extent remedied of recent years by the issue of several works of more moderate dimensions and price. Between the small elementary text- book and the still large and comparatively costly work of reference, however, there yet remains a considerable gap, which it has been the Authoi^s endeavour in this volume to fill The best authorities have been freely consulted and, with due acknowledgment, laid under contribution; while the latest methods of working and the most modem machinery have been described, with the object of presenting an up-to-date account of the important industry under consideration. Since the publication of the excellent treatise by Jonathan Hyslop^ thirty years ago, no text-book dealing to any extent with Scottish practice has, so far as the Author is aware, been published. As his experience has been gained largely in Scotland, he has attempted to remedy this omission, and it is to this that the occasional occurrence of a few Scotch words or phrases must be attributed, although these have been avoided, as far as possible, when reference is made to methods prevailing elsewhere. Less attention has been paid to literary style and elegance than to the production of a thoroughly practical and plainly worded text-book, designed not only to aid those endeavouring to qualify themselves for positions as colliery managers and other responsible officials, but also as a daily guide and reference-book for all engaged in and about the Collieiy. The Author gratefully expresses his indebtedness to other sources, which, except in oases where a difficulty in tracing the authorship VI PRBFAOS. ivas ezperienoed, he has acknowledged in the text. The works of Hughes on Coal Mining, and of Foster on Ore and Stone Mining, ImAve been quoted, and a few of the illustrations have been borrowed CK*om those works. The Author has further to acknowledge the kind assistance of ^/£r John Dodds, who helped to prepare many of the drawings for the ^v^ork. He also desires to express his thanks to the publishers for tbe pains they have taken botli as regards the text and the illustrations. G. L. KERR. Bo'NEfiS, K.B., September, 1900. NOTE TO P^OURTH EDITION. In issuing this new edition advantage has been taken to thoroughly revise and extend the work. Over forty pages of new matter have been introduced, and the whole rearranged. A considerable number of new illustrations have been added, while at the same time a number included in former editions have been deleted owing to their having become obsolete in modem mining practice. With the additions and improvements that have been made in the present edition, the author hopes that its use- fulness will be correspondingly increased. O. L. K. Olaboow, October 1905. CONTENTS. CHAPTER I. THE 80UKCE8 AND NATUBII OF GOAL, PAOl . 1-11 Introdnctorj, . Definition of the term ' rock,' . Division of rocks. Stratification, . Cleavage, Inclination of strata. Dislocations and faults, Division of coal-measures, 1 1 1 4 2 2 2 . 8,4 4 Coal in other formatiuns, Formation of coal-fields, Ori^n of coal, . Definition of coal, Classification of coal, . Selection of coal. Calorific power of ooal, . 6 5 6 6 6 8 . 9-11 CHAPTER II. THE flEABOH FOB GOAL, , 12-29 Boring, .... Methods of boring. Chisels or bits, . Rods, • Braoehead, Sludger, B^he, . Brakestaff, Preliminary operationit, Lining the bore-hole, . 12 IS 13 18 14 14 15 15 15 18 Speed of boring. Cost of boring, • Japanese method of boring, Cost of boring plant, Mather & Platrs system, Diamond boring, Davis Calyx Drill, Other objects of boring, Surveying bore-holes, . 19 20 20 20 21 28 26 26 29 CHAPTER III. SINEINO, Preliminary oonsiderations, Commencing operations, Sinking and walling simultane ously, Tubbing, Coffering, Cost of sinking, . Sinking rectangular shafts, Special methods, • Pile-driving, Brick drums, . 30 32 85 38 41 42 48 47 47 4S Iron cvlindera, . Trigers method, ICind-Chaudron method, Lippman's method, Pattberg system, Gobert's method, Koch's system, . Poetsch's method, Accessories to sinking. Ventilation, sinking pits, Enlarging shafts, 30-70 50 53 54 59 59 62 63 64 65 68 69 vu viii CONTENTS. CHAPTER IV. PAOI EXFL081YES, . • . 71-86 Definition, • 71 Detonators, • < 79 1 Classification, . 71 Precantions against fire-damp Gnnpowder, 72 explosions, . ■ 80 i Chlorate mixtnre«, 78 Safety fuses, • 1 80 Nitro • compounds contaiDing nitro-gfycerine, Safety explosives, Firing shots hy electricity, PreTention of name communica- 81 78 74 tion, • 1 84 Nitro-oompounds not containing Cost of blasting. • t 85 nitro-glyoerine, 77 CHAPTER V. MEOHANIOAL WEDGES, BOOK DBHiLS, AND OOAL-OUTTINO MAOHINES, . • • • • . 87-96 Mechanical wedges, 87 Machine-power drills. 92 Elliott wedge, . 87 Darlington drill. 98 Burnett's wedse. Hydraulic wedges. 87 Adelaide ,, 94 89 IngersoU „ 96 Bock drills, 91 1 CHAPTER VL OOAL-OUTTIKO B7 MAOHINEBY, » 97-118 Introductory, . 97 Hurd bar machine. • 109 Classification of machines, 99 Goolden bar machine • 109 Heading machines, 99 PercussiTS machines. « 1 109 Disc machines, . 100 IngersoU-Sergeant machine, 111 Gillot k Copley machine, BigK k Meiklejohn machine. 100 Harrison II 112 100 Morgan-Gardner It • 118 Clarke k Steavenson ,, 102 Champion i« « lis Diamoud „ 104 Choice of machine, • 1 114 Anderson-Boyes ,, 104 Conditions suitable for coal Jeflfrey „ 106 cutters, • 1 115 Chain . 106 Timbering at machine face. 116 Jeffrey chain „ 107 Labour for machine cutting. 116 Cham shearing „ 108 Motiye power for machines, 117 Bar machines, • 108 Cost of machine installations, . 118 CHAPTER VII. TBAN8MI8SI0N OF POWEB, . Location of machinery, . 119 Steam, . . . . 119 Compressed air. 121 Valves for compressors, 124 Losses in air compressing. 124 Electricity, . 127 Electric cables, . 127 Fixing underground cables, . 128 Shaft cables. . 128 Junction boxes, . 129 Generators or dynamos. Motors, . Electrical plant failures. Test of hauling engines. Electric pumping. Advantages of electricity, Disadvantaj^es of electricity, Cost of yanotts systems, Electrical terms, 119-136 129 180 181 188 188 184 184 185 185 CONTENTS. IX CHAPTER Vin. MOBES OF WOBXING, PAOS 187-174 Choice of methods, 187 Panel system, . 151 LoDgwall, 187 Special methods, 152 Pillar asd stall, 144 Spontaneous combustion, Working highly inclined seams 157 Size of bottom pillar, . 145 , 159 Width of stalls. 148 Double and single stall, 169 ExtractiDg pillars, 149 Working thick seams, . 172 { CHAPTER TX. TIHItKRTNG BOADWAYS, . 175-201 Necessity for timbering, 175 Iron or steel props. 186 Timber, 177 Steel or iron sets. 186 Methods of support. Driving through loose ground, . 177 Brick walls and girders, 190 182 Strength of timber, 195 Brickwork supports, 184 FormulsB for strength of timber, , 197 Iron or steel supports, . 185 Preservation of timber, . 199 CHAPTER X. WDTDZNG COAIi, . 202-246 Preliminary, 202 Reducing strain on ropes, 223 Pit-head frames, 202 Cage guides. 224 Iron or steel frames, 206 Cages, . . . . 228 Winding engines, 207 Cage speeds. 281 „ ropes, . 212 Pit-head pulleys, 231 Iron ropes. Care of ropes, . 218 Drums, 232 214 Safety hooks, . 284 Rope tappings, . 215 Safety cages. 237 Strength of ropes, 216 Cage props or keps. 239 Counterbalancmg, 219 Automatic apparatus, . 242 Conical drums, • . 220 ' The visor, . 243 Koepe's system, . i 221 Size of winding engine, . CHAPTER XL 248 HAULAGE, . . . S M 7-293 Classification of methods. 247 Horse traction, . 252 Roads, .... 247 Feeding of horses, 253 Rails, .... 247 Cost of horse haulage, . 256 Laying roads, . Tubs, .... 248 Inclines, 256 248 Machine haulage. 265 Arrangements of pit-bottom. 251 Cost of haulage. Haulage problems, 290 Haulage, 252 291 c ;hapter xil PUMPING, .5 {94-849 Preliminary, 294 Pumping engines, 319 Pumps, . 296 Pulsometer pumps, 834 Pump Talves, , 801 Centrifugal pumjis, . 836 Buckets, 802 Sinking pump, . Air vessels, 839 Plungers, . 808 841 Pump-rods, 804 'Duty' of pumps. 843 Sise of rods, 808 Pumping problems. 846 Plant required, 818 X • CONTfiNTS. CHAPTER XIII. PAQE VENTILATION, . . 350-414 Gases present in mineSi 850 Speed of fans, . 385 Carbon dioxide, 855 Cost of ,, . 385 ,, monoxide, 857 Guiding air currents, . 386 Sulphuretted hydrogen, Carouretted ,, 358 Brattice, 390 858 Laws of air currents. 392 Natural ventilation, 364 Reducing friction, 396 Waterfall „ 366 Instruments used. . 402 Furnace ,, 866 Coal dust. 404 Mechanical ,, 373 Ventilation problems, . 412 Fans, . 373 CHAPTER XIV. SAFETY LAMPS, . Definition, 415 Davy lamp, 416 Clanny lamp, . Stephenson lamp. 416 417 Marsaut ,, 417 Mueseler ,, 418 Gray . 419 Wolf 420 Wolf-Dahlmanu lamp, . 421 Evan Evan's ,, 421 Evan Thomas i, . 422 Fire-damp indicators, . 423 Hydrogen indicator, Stokes s ,, Pieler lamp, Chesnean lamp, . Electric lamps, . Construction of lamp. Lighting power. Cost of upkeep, . Protector lock, . Testing lamps, . Trimming and cleaning. Filling and lighting, 415-434 428 424 424 425 426 427 427 428 429 430 433 434 CHAPTER XV. SUBFAOE AEBANGEMENT8, COAL CLEANING, EIC, 435-459 Siding accommodation, . . 435 Coal cleaning, . 447 Boilers, . . 436 Screening, 447 Banking out. . 440 Jigging screens. Coal washing, . 448 Tipplers, . 442 448 Travelling belts, 444 Varieties of washern, 450 Elevators, 446 Cost of washing, 459 CHAPTER XVr. 8T7BVETING, LEVELLING, AND PLANS, Definition, Magnetic variations. Dip, Determining the Meridian, Setting out Meridian line. Colliery plans, . Underground surveying. Vernier compass, Measurements, . , on inclines, INDEX, . 460 Stepping the chain. 474 461 Protractors, 475 464 Plotting by co-ordinates, 476 465 ,, chords, 479 . 465 Calculation of areas. 480 . 466 Levelling, 483 . 468 Datum line. 486 . 470 Booking the levels. 486 . 472 Plotting levels, . 48S . 473 Problems, 488 • § 9 - * t 495 PRACTICAL COAL-MINING. GHAFTBE I. THE SOURCES AND NATURE OF COAL. Introductory. — ^The art of mining fjid science of geology are so closely related that it has become almost impossible to write a treatise on the former without referring to the latter. Text-books on coal-mining are therefore usually prefaced by a short introductory chapter on geology, and the present volume will, in this respect^ conform to established custom. The earth is composed of mineral matter in yarious combinations which are included under the general term of rock. It is an oblate spheroid in shape — ^that is, a sphere which has been flattened at the poles. It was at one time supposed to consist of a hard, solid, outer crust 10 or 12 miles thick, and an interior of molten material at a very high temperature. This theory was deduced from the increase in temperature observed in subterranean workings, and from the fact that molten lava is thrown out by volcanoes during eruption ; but^ according to Lord Kelvin, it is much more probable that the earth is a rigid mass from surface to centre with the properties of a solid. Definition of the term Bock.* — *' A rock may be defined as a mass of matter composed of one or more simple minerals, having usually a variable chemical composition with no necessarily symmetrical external form, and ranging in cohesion from mere loose debris to the most compact stone. Granite, sandstone, mud, peat, etc., are all reooffnised as rocks.'' Dmsion of Bocks. — Rocks are divided into three classes, viz., aqueous, igneous, and metamorphic; or into two, stratified and unstratified. Aquious rocks are those which have been deposited where we now find them, by the agency of water. They are generally in layers or beds lying parallel to each other, and are often termed sedimentary * Text-book of Oeology, p. 67, by Sir Arehibftld Geikie. 2 PRACTICAL COAL-MINING. rocks or deposits. Igneovs rocks are those which have been subjected to the action of heat and retain no traces of stratification or bedding. Metamorphic rocks are rocks in which a crystalline rearrangement of the materials has taken place. They are sometimes called altered rocks. Marble is one of the best and most representative specimens of a rock of this class. Aqueous or sedimentary rocks are deposited in definite layers or beds, this arrangement being termed siratification. When the deposits form very thin layers, such as occur in shale, they are said to be laminated. Cleavage. — Cleavage is the term applied to the tendency of rocks and minerals to split along certain planes other than those of stratification, which occurs in stratified rocks and which tends to break the rock up into more or less cubical blocks. Generally when a rock is much intersected by cleavage planes, it loses its property of splitting along the bedding planes. Cleavage planes are said to be due to great pressure. Inclination of Strata. — The strata which compose the crust of the earth were no doubt deposited in horizontal layers ; but only limited areas are now found in that position. In all parts of the world beds of rock are usually inclined at a greater or less * angle of dip ' to the horizon, hence they usually come to the suHace at some point, and when this happens it is termed the outcrop of the bed. In flat, low-lying stretches of country few outcrops may be seen, while in hilly country, especially where the district is intersected by ravines and river-courses, the strata may be seen to outcrop frequently. It is in such positions that rocks can be most easily and advantageously studied. Dip. — If a bed of rock be inclined to the horizon it is said to dip ; the point of the compass to which it inclines is called the direction of dip, and the angle, or degree of deviation, which the strata make with the horizon is termed tlie amount, or angle of dip. This angle is expressed in degrees, and is usually measured by an instrument called the clinometer. Strike, — The prolongation of the strata in a line of bearing at a right angle to the dip is called the strike. Thus, if the dip be due north and south, the strike will be due east and west. Sometimes the strike and outcrop coincide, as in the case of vertical beds, but more usually it varies with the stratigraphical contour of the beds. Anticlinal and Synclinal, — In many parts of the world the strata are contorted and bent into folds. The French and Belgian coal-fields furnish examples of such distortion. Where the strata dip away from an axis so as to form an arch or saddle, they are termed ^ anticlinal,^ Where they dip towards an axis, forming a trough or basin, they are called * synclinal* (see 6g. 1). Dislocations, Faults, and Dykes. — Hocks are liable to many dis- turbances and to fracture. Such fractures may be either simple THE SOURCES AND NATURE OF COAL. fissures or rents in the rocks without any displacement on either side (joints), or the strata may have a greater or less amount of displacement {faults). In the largest proportion of cases there are hoth fracture and displacement in the beds, the rents becoming both * fissures ' and * faults ' (see fig- 2). Faults may vary in width from JklUdMiJ^ ^fUfMli^ x.<: Fio. 1. Fig. 2.— Fault mere sharply defined lines with very little displacement up to gaps of many yards in width and hundreds of yanls displacement. All the British coal-fields are traversed by many of these faults, the main faults in nearly all cases running almost due east and west. Sometimes, however, faults branch off or run into one another. The inclination which a fault makes with the vertical is termed the hade, and the line of fracture the vees of a fault. The degree of vertical displacement is known as the amount of throw. Faults are sometimes vertical, but are generally inclined. The largest faults, ue, those which have the greatest vertical displacement, commonly slope at high angles. Those of only a few feet displacement may be inclined at angles as small as 18° or 20"" from the horizon, but this is exceptional. A fault is termed a down-thrown fault if the observer is looking from the higher to the lower level of displacement ; and an up-throw fault if in the opposite direction. Faults may be either Normal, Reversed (fig. 3), or Overlap, Trough (fig. 4), or Step Faults. When Snti ^^^? Fio. 8.— Reversed Fault Fio. 4.— Trough Fault parallel faults run in the direction of the strike, and have their down-throw with the dip, this tends to prevent certain outcrops from appearing. On the other hand, a succession of step faults, with down-throws against the dip, may cause the same beds to crop out again and again, and hence be mistaken for a number of different seams. When a bed has, from some cause, had a portion denuded or worn away, it is known as a dumb fault, or washrout. The action of water is the most frequent cause of a wash-out. 4 PRACTICAL COAL-MINING. The term dyke is often confused with the t&nnfaidt hj miners, and taken to mean the same thing. When a fault occurs there is displacement of the strata; but a dyke is usually unaccompanied by any displacement. Dykes are wall- like masses of rock which ti-averse strata in succession from unknown depths- ^and appear in many instances at the surface. They usually consist of basalt or allied rock, and are of volcanic origin, having apparently been intruded' while in a liquid state into fractures. Dykes affect very materially the quality of the coal intersected by them, which is * burnt ' into a soft, cindery, and sooty state, or altered into a hard and incombustible substance. The distance that the coal-seam is affected on either side of a dyke is usually about two-thirds of its width. Dykes vary in width from less than a foot to 70 ft. and upwards. It is not unusual for them to run in nearly straight courses for many miles. Sometimes they occur along the lines of a fault, but very often they are unconnected with faults in any way. Frequently they are found to cross faults without being in the least deflected out of their course thereby. Division of Rocks into Groups. — The rocks forming the crust of the earth in the British Isles have been divided into five main groups. They are disposed in the following order : n i. n i,rr ^' i Recent and Pre-historic. Quaternary or Post-Tertiary | pieigtocene, (Pliocene. Eocene. ( Cretaceoua. Secondary or Meaozoic -I Jarasaio. \ Triaasic. ' Permian. Carboniferoas. Devonian and Old Red Sandstone. Silurian. , Cambrian. A^i«».» «. A.^;« / Primitive Schists. Arch«an or Azoic | ^.^^.^ ^^^ ^^j^^^ CiysUlline Rocks. Primary or Palaeozoic Goal-measures. — The formation which has the greatest interest for the coal-miner in this country is the Carboniferous, for it is in this formation that coal is found most abundantly. It consists of three divisions of strata, viz. : — Coal-measures, Millstone Grit, and Carboniferous Limestone. The upper division or Coal-measures are the strata where coal- seams are most abundantly found. In the English coal-fields, very few workable seams are found below these measures. The millstone grit is usually composed of coarse yellow sandstones, flagstones, shales, and a few thin seams of coal. In the Scotch ooal-fields valuable seams of coal and ironstone are found below the THE SOURCSS AND KATTTRE OF COAL. 5 millstone grit. In the Carboniferous formation of Scotland, the following four divisions are made : — Coal-measares Carboniferous Limestone " Consisting of (a) an upper series of red and purple sandstones and shales enclosing thin coal-seams^ and (in Ayrshire and Fife- shire) thin limestone bands ; (6) the productive coal-measures, consisting of white and grey sandstones, shales, coals, fireclays, and ironstones, but no limestone. Millstone Qrit ( Coarse thick sandstones with shales, fireclays, thin seams of coal, or Moor Bock \ clayband ironstone, and, occasionally, beds of limestone. ' This series is often sub-divided into (a) thick sandstones and beds of shale with three varieties of limestones and some coals ; (5) a group of ordinary coal-measures veiy similar to the upper coal-measures, and containing valuable seams of coal and iron- stone, but no limestone ; (e) sandstones, limestones, shales, with some coals and ironstones. (This series may be sub-divided into (a) the upper group, consisting of sandstones, shales, oil shales, some very inferior coals, iron- stones, and limestones ; (6) the beds lying below, extending to the base of the carboniferous rocks. It will be seen from the above that the coal-measures in Scotland difiTer greatly from those of England, inasmuch as a large proportion of the coal in the Scotch coal-fields is found below the millstone grit, while in the English coal-fields very few valuable seams are met with below that formation. Coal found in other Formationg.— It has been shown that coal is most abundantly found in the Carboniferous strata, but it is not entirely confined to that formation, being often found in others — although such coal is seldom of much value compared with that of the coal-measures— both above and below the Carboniferous forma- tion. In New South Wales coal is got from the Devonian series of rocks ; at Bonn, in Germany, and at Bovey Tracey, in Devonshire, the coal-beds are, presumably, of Miocene age ; the brown coals of New 2jealand and Australia are believed to be late Tertiary deposits, while at Brora, in the North of Scotland, coal is found in the Jurassic formation. Nearly all these are, however, lignites as distinguished from the true coals found in the Carboniferous formation. Roeks and Minerals associated with Coal, — Coal when found is generally associated with sandstones, shale or blaes — known amongst miners as bind — limestone, fireclay, ganister, ironstones, iron pyrites, and in Scotland, oil-shales. Most coal seams rest on a bed of fire- clay ; in some districts this under-bed takes the form of ganister. Pormation of Coal-fields.— It is a noticeable characteristic of coal-fields that they take the form of a basin, dipping from all sides towards a central axis. Hence we get the seams cropping out frequently at the surface, which allows of large areas being easily reached and worked. Were it not that coal-fields assume this shape a large part of our coal supply would inevitably be found at too great a depth to be workable. 6 PBACnCAL OOAL-MINIKO. Origin of GoaL — Regarding the origin of coal numerous theories are held, one being that it was formed in the position in which we now find it, and is the product of vast forests which grew, flourished, and decayed on the site of our present coal-fields. Another is that it was brought into its present position by what is termed the ' drift ' process, the forests being supposed to have flourished and decayed in one part of the world, while the accumulated * humus ' was swept into its present position by the agency of water or ice. While the * drift' theory may explain the origin of a few isolated deposits, there is little doubt that the first mentioned theory is correct. Definition of CoaL — Coal is a substance which it is easier to recognise than to define. Nearly everybody is familiar with the appearance and uses of this common mineral, but its definition is attended with several difiiculties. Dr Percy defines it as : "A solid, stratified, mineral, combustible substance, varying from dark brown to black, opaque, except in extremely thin slices, brittle, not fusible without decomposition." Sir Archibald Geikie defines coal as : " A compact, brittle, velvet- black to pitch-black, iron-black, or dull, sometimes brownish rock, with a greyish-black or brown streak, and in some varieties a dis- tinctly cubical cleavage, in others a conchoidal fracture. It contains from 75 to 90 per cent, of carbon and a small percentage of sulphur generally combined with iron. It has a specific gravity of I '2 to 1 '35, and bums with comparative readiness, giving a clear flame and a strong aromatic or bituminous smell, some varieties fusing and caking into cinder, others burning away to a mere white or red ash." Or more shortly : " Coal is composed of compressed and mineralised vegetation." GXassification of CoaL — The varieties of coal may be classified as — (1) Anthracite, or smokeless coal. (2) Steam, free barnin^, or dry coal. (3) Bituminous, or cakmg coal. (4) Cannel, parrot, or gas coal, including the Boghead variety sometimes called Torbanite. (5) Lignite, or brown coal. All these varieties have had a common origin ; they are all accumula- tions of ancient vegetation which has undergone chemical change under certain conditions. In the 'lignite' or 'brown' coal this change has been less complete than in the others. Anthracite, sometimes also called 'blind-' and ' stone-' coal, has usually a brilliant black lustre, breaks with a conchoidal fracture, and does not soil the fingers when handled. It has been supposed that it has, at some period, undergone a sort of natural coking process, under the influence of subterranean heat, and that this has driven off* a large proportion of the hydrogen, oxygen, and nitrogen it originally contained. Anthracite gives off little or no smoke and is difficult to ignite, but when burning gives out intense heat It THB SOURCES AND NATURE OF COAL. 7 consists almost entirely of carbon, the best qualities containing 90 to 95 per cent, with 5 to 10 per cent, of hydrogen, oxygen, and nitrogen. Steam coal closely resembles bitmninous coal, from which it differs only in being slightly harder, lighter, and more compact. It does not cake when heated, however, and it is practically smokeless. Its specific gravity varies from 1*27 to 1*30. On analysis it yields approximately 89 per cent, of carbon, 4*5 per cent, of hydrogen, 3 per cent, of oxygen and nitrogen, and 3*5 per cent, of ash. Bituminous coa/j also known as */ree burning,' * smoking,' or ^flaming coal,' when ignited, bums readily with a yellow flame, giving off smoke freely. On heating it swells into a pasty, bitumen-like mass which ultimately becomes solid. Bituminous coals are misnamed, as they contain no true bitumen. There are several varieties of bituminous coal, which are distinguished according to their mode of burning, which depends chiefly on the relative proportions of carbon, oxygen, and hydrogen they contain. Steam coal approaches anthra- cite in its properties. Dry or non-caking coal is another variety ; it does not possess the property of caking which makes coal so valuable for household purposes. Non-caking coals are generally hard and compact, and when in a fine powdery state do not cohere when heated. Oannel is generally classed as a variety of bituminous coal, although it is not a true coal, as it contains a certain amount of argUlaceous matter, and sometimes even passes into shale or iron- stone. Cannel or gas coal differs a good deal in appearance from ordinary bituminous coal, being of a dull, lustreless, black colour, not splitting readily into thin layers, and generally devoid of vege- table structure under the microscope. The best qualities of cannel are of a tough nature and can be cut readily with a knife ; ornaments are frequently made from cannel of this kind. An analysis showed — Volatile matter (containing '58 of Sulphur), . . 40*28 per cent. i Carbon, 49 40) Sulphur, 0*29 > . . .56*22 ,, Ash, 6-58 ) Water, expelled at 212* Fahr. 3*50 „ 100-00 Cannel coal contains a comparatively large percentage of oxygen and hydrogen, and it is therefore valuable for the manufacture of coal gas or paraffin oil, and is only distinguished from the bituminous shales now so extensively used in the manufacture of paraffin by the much smaller proportion of ash which it contains. The yield of gas from cannel coal varies from 10,500 to 13,500 cubic feet per ton^ and from bituminous coal, from 9000 to 10,000 cubic feet. Boghead, or torbanite, is a mineral occurring at Boghead, near 8 PRACTICAL COAL-MINING, Bathgate, in Scotland. It has long smce been practically exhausted. The mineral was brownish-black, and had a specific gravity of about 1*15. It contained 63 per cent, of carbon, 9 per cent, of hydrogen, 20 per cent, of ash, and 8 per cent, of oxygen and hydrogen. It yielded 15,000 cubic feet of gas, and about 70 to 80 gallons of oil per ton. Lignite or Brown Coal, — 'Lignite' or * brown' coal is the term usually applied to deposits of more recent origin than coals found in the carboniferous formation, to which formation true coal belongs. Lignites vaiy in colour from a light earthy brown to a deep lustrous black, undistinguishable from ordinary bituminous coal. They contain 50 to 70 per cent, of carbon. In New Zealand the coal worked is of the lignite variety, and is not of a very high quality. Brown coals proper usually contain a larger percentage of carbon and a smaller percentage of oxygen than the true lignites. The general composition of lignites and brown coal may be seen from the following analyses : — Lignite from Bovey Tracey, It f» Cologne, Brown coal from Hungary, . ,1 ,, ,, Tasmania, ,, ,, ,, Auckland, irbon. Hydrogen. Oxygen and Nitrogen. 67-9 6*8 26*8 67-0 6-8 27-7 72-5 6-4 221 71-9 5*6 22-5 72-2 5-4 22*4 The following table shows the various changes through which coal passes during its transition from wood to anthracite : — Weight of 1 cubic foot mlbs. Carbon I)er cent Hydrogen percent Oxygen an ifitrogeo percent Wood, average, . 80 50-29 6*09 48-62 Peat, 60 60*88 5*89 88 28 Lignite, „ . . . 70 67*43 5*59 26*98 Brown coal, average, . 76 72-92 6*4 21-58 BituminouH coal, average, . 80 88-48 5-84 11-18 Anthracite, average, . 90 95*85 2-47 2*18 Selection of Coal, — Dr Percy says that the only sure guide in the selection of coal for any purpose is to make a practical trial on a large scale. A good deal of information may, however, be obtained from reliable chemical analyses, but as a rule the thermal value of a fuel, as determined by a physical test, is never even approximately realised in practice. An anthracite coal with no gas or flame may be suitable for one purpose, while a bituminous coal full of rich smoky gas may be most economical under other conditions. In any fuel large quantities of ash are objectionable, as they reduce the quantity of available combustible material per ton of fuel, and increase labour in handling both fuel and ash, while the fires require more frequent cleaning, THE SOURCES AND NATUBE OF COAL. 9 which entails a reduction in the efficiency of the boiler by the chilling influence of the cold air admitted during the process. A large percentage of moisture is also objectionable, as a portion of the calorific power of the coal is unproductively expended in evaporating the combined water. The following analyses show the composition of the two varieties of good burning coal : — Caking Coal. Non-caking Coal. Carbon, 75 per cent. Hydrogen. . 4 ,, Oxvgen, . 16 „ Ash, . • 8 ,, Water, . 6 8 „ 76 per cent. 4-8 „ 16 8-8 „ 5-4 „ Coals are also sometimes classed as High Quality and Low Quality ooal, as shown by the following analyses * : — High Quality Coals. Low Quality Coals. Anthra- • M Semi- bitumin- Bitumin- Anthra- Semi- bitumin- Bitumi ate. 0U& ous. cite. ous. ous. Fixed carbon, 88-6 76-6 58*5 76 0 67-0 46-6 Volatile matter, 5-0 18 0 40-0 6-0 16-0 84 0 Sulphur, 0-5 0-6 0-6 2-0 8-0 3-5 Ash, . 6-0 6-0 6-0 16-0 12-0 12-0 Water, 1-0 1-0 1-0 2-0 8*0 4-0 Calorific Power of Coal. — ^Modem requirements now demand the most economic generation of heat for a given expenditure of fuel, no matter to what purpose the coal is put. As already stated, the thermal value of fuel is not easily ascertained with any high degree oi accuracy by chemical or physical tests, and only approximate values can be looked for. The simplest method of finding the calorific power is by using the instrument know as Thomson's calorimeter, which is largely adopted for this purpose. The principles upon which the test is based are : — (1) That the latent heat of steam is equal to 967" Fahr., and (2) that coal or other fuel burned in pure oxygen evolves the same amount of heat as when completely consumed in atmospheric air. The test is carried out as follows : A measured weight of fuel is dried, finely powdered, and intimately mixed with the necessary propor- tions of a mixture consisting of three parts of potassium chlorate and one part of potassium nitrate. This mixture, which will bum freely without a supply of air, is placed in a copper cylinder b (fig. 5), which is primed with a fuse. This cylinder is placed within the copper combustion vessel c, and is then immersed in a glass jar a containing a known weight of w^ater. The fuse, in the small cylinder b contain- ing the chlorate mixture, is lighted, and the appliance is plunged into the glass cylinder containing the water, and is covered by the * Pradieal Engineen' Pocket Book, 1897, p. 324. 10 PRACTICAL COAL-MINIKQ. second copper cylinder c, the cock at d being shut. After a few seconds the fuse ignites the mixture of coal and potash, and the products of combiiBtion, paasing through the water in a finely divided state, com- muiucate the whole of their heat to the water. The temperature of the latter is carefully noted at the commencement and end of the test, and it is only necessary to multiply the weight of water by the number of degrees of heat communicated to it to find the calorific value of the fuel. The amount of water capable of being converted into Htoam per pound of fuel burnt is directly as the elevation of the temperature ; thus, if the ther- mometer showed a rise of 7*6*, then one pound offiKlvmUd eoapOTOie To lbs. of water. Tables Fra & -Thomsons ^ facilitate calculation are supplied with each 'cWorimet«r. instrument. The theoretical evaporative power of fuel may also be calculated from the ultimate analyses by the formula : — P=16J<; + 4-28) <-?)) Where C = weight of carbon in 1 lb. of fnel. H= ,, hjdiogen ,, 0= ,, oiygen ,, P = lbs. of water at 212* F.,eonvGrted into steam &t 212* F. per lb. of fuel. As an example, in the analyses of the caking coal already given the carbon was 75 per cent., the hydrogen 4 per cent., and the oiygen 16 per cent. These would be in the ratio of '75, 01, and 16 ; then by applying the above formula we have — P=15|-76 + 4-28r04-^U=15{-7B + (4-28x-O2)}=16K'88B8 = 12-631ba. widely Calorific Power of D17 Coal free from Asb (in Natnre of Coal. British thertiul nnib). Lignite, 13,887 12,584 18,253 Brown Coal, 11,340-14.220 Caking Coal, 15,804 16,108 „ 15,661 17,319 Anthracite, 17,021 Basin of Donetz, Russia, . ,, 14,868 * Cvai, U* Bittajy and Uia, p. 2ao. THS SOURCES AND NATURB OF GOAL. 11 From recent experiments made on Scotch coals the calorific power and specific gravity are shown in the following table : — Calorific Value Specific Gravity. (B.T.U.) 1-266 18,464 1-261 13,662 1*292 13,365 1-290 13,266 1-286 13,464 1-291 13,563 1*806 14,157 1-276 14,058 Ell, . Main, SpUnt, Qas, Virgiij, Kilsyth Hanghrigg, Bannockbum Main, Kilsyth Coking, The calorific value of a pound of fuel in B.T.U. can be calculated from the formula : a;=U5C + 620(H-iO), where C, H, and 0 represent the percentages of oarbon, hydrogen, and oxygen present as determined by analysis. CHAPTER II. THE SEARCH FOR COAL. Boring. — The search for coal in an unknown district is the appli- cation of geology to practical uses. In such a search all available means are taken to obtain information, such as the examination of quarries, beds of rivers, and railway cuttings. Even the ploughing of fields has often led to the discovery of the presence of ooal when there were no other indications. An examination carefully carried out in any district will reveal whether the strata belong to the coal-bearing formation or not. The discovery of a few fossils, such as sigillaria or stigmaria, will at once identify the rocks ; or an ' outcrop ' of coal may be dis- covered at the surface, but this is not often the case, particularly if the coal-bearing strata have been deeply overlaid by newer formations. In such circumstances resort must be had to boring to decide whether coal be present or not. Boring is the means adopted to determine the existence of beds of minerals, such as ironstone, coal, and salt, lying below the surface of the earth, and to obtain information respecting their position, thickness, and quality. The uses of bore-holes vary considerably, and may be stated as follows : — To reach a mineral deposit in order to ascertain its nature, depth from the surface, strike, etc To ascertain the nature of the subjacent rocks for engineering purpoaes, such as railways, canal cuttings, bridges, etc. To obtain liquids such as ordinary water, mineral water, brine or petroleum. To make absorbent wells in dry and porous strata. To obtain gases, such as natural inflammable gas, carbonic acid gas or va|)ours containing boric acid. To drain off water or gas from mine workings. To make passages for conveying water to underground fires or power into underground workings. To install signal wires or speaking tubes. To sink holes for lightning conductors, house-lifts, or piles. To introduce cement into unsound foundations to strengthen them, and also into mine workings to dam water. To sink mine shafts, J2 (1) Percussive Boring With Rods. With Ropes. THE SEARCH FOR COAL. 13 In a field of coal it is usual to put down a series of bore-holes for the purpose of obtaining a correct section of the strata passed through ; of finding the depth of a seam or seams from the surface, the thickness, quality, and number of seams, the chemical properties of the coal and the nature of the roof and pavement; and of ascertaining the inclination of the strata, as also the number and size of ' faults ' in the field. In establishing the existence of dykes or faults underground, bore-holes sometimes save time and money which might otherwise be wasted in exploring by means of shafts, particularly when the ' Tees ' of the fault is nearly vertical or ill-defined, and it is difficult to determine whether it is an up-throw or a down-throw fault. By their aid the gradient of a road that would intersect the dislocated seam can {dso be determined. Methods of Boriiig. — There are two chief methods of boring, viz., percussive and rotary. These may be again sub-divided thus : — ' Ordinary method of chipping and removing debris. Japanese method of ' plunging ' without removing debris. ' Chinese and other methods with a spring ^le. Ordinary method employed in American oil districts. , Special methods, such as Mather k Piatt's and others. (2) Rotary / Boring with augers in soft material. Boring \ Diamond rock-orill boring. Hydraulic methods are applied to both systems of boring. The percussive method is largely adopted for shallow bore-holes, or in soft, easily worked rock. It is commonly carried out by means of free-falling tools, which chip or cut the rock into angular fragments. The rotary method grinds the rock into powder, or can be made to cut out a solid core. The commonest method of boring, for depths of 5 fms. or more, is carried out by means of a steel chisel screwed into an iron rod, and suspended from a spring-pole. The tools used for a bore-hole in ordinary strata are chisels, rods, bracehead, augers, and sludgers for extracting the loose material ; tools for dressing the sides of the bore-hole and for extracting broken rods or chisels : also keys for screwing and holding the rods, and tubes for lining the holes. ChlselB or Bite. — The form, sharpness, and temper of the cutting tool employed vary according to the rock which has to be cut through. Various chisels are in use : flat or straight- edged for ordinary strata, ▼ or diamond-point chisels for hard rock ; the T chisel for gravel ; while others, with cutting edges shaped like an S or Z, are used for different kinds of work, but these chisels are difficult to sharpen and maintain in good order. For soft groimd, such as clay or peat, augers are used. The chisels are 1 8 in. to 24 in. long, 1 in. to 2 in. diameter, and 2 in. to 3 or 4 in. in breadth of face. They are made of the best steel, and weigh from 3 to 4^ lbs. each. Fig. 6 shows some of the forms used. Eods. — The rods are made of wood or iron, more commonly the 14 PBACnCAL COAL-MININO. $ latter, the best material being selected. They are octagonal, round, or square in section. Ordinary rods are J in. to 1^ in. square, | in. and 1 in. ; they are made in lengths of 1^ ft. to 10 or 12 ft. j the bottom rod is alwa3rs about 3 ft. long. The usual mode of connecting the rods is by a screw-joint (fig. 7). Iron rods 1 in. square weigh about 10 lbs. per yard. Wooden rods are generally made in 20 to 30 ft. lengths of pitch pine, and not less than 2^ in. square. The sections are joined by ordinary butt, or scarf joints and iron strapping plates. Braoehead. — For shallow holes boring can be accomplished by the single bracehead, actuated by two or more men, for a distance of 10 or 15 yds. ; beyond that depth a double bracehead is used until 20 or 30 yds. is reached, when a spring-pole and windlass will be required. The single bracehead is made with a wooden handle about 3 ft. long and 3 in. diameter at the centre, and tapers I O i i] Flo. 6.— Chisels. Fio. 7.-— Rods. at each end. The centre is furnished with an eye made of iron, to which the rods are attached (fig. 8). Sludger. — The sludger is usually a tube 3 to 10 ft. in length, and of a diameter suitable for the bore-hole. It is provided with an ordinary clack or ball valve at the bottom (fig. 9). When it is required to clear the bore-hole, the sludger is lowered, and worked up and down a few times at the bottom in order to fill it with the broken material ; it is then drawn to the surface, and the contents carefully examined. THE 8KABCH ?0R GOAL. 15 The B6che is the tool used for extracting broken rods in cases of fracture. It is about 2 ft. loug, and hollow for about 16 in. at the lower end, the diameter of the opening at the bottom being about IJ in. and tapering to | in. diameter (tig. 10). The Brake^taff is a lever of pitch pine, 10 to 14 ft. long, having a fulcrum 1 J ft. to 2 ft. from the end next the rods. At one end is placed an iron hook, a rope being attached to it to enable the men to give it motion (fig. 12). Preliminaiy OperationB. — When boring ia about to be commenced, a platform of wood, 2 or 3 ft. square and 3 in. thick, is laid on the ground, and a hole Ixired in the centre for the rods to pass through into the bore-hole. Short lengths of rods, 18 in. to 3 ft., are used at the beginning until the hole attains sufficient depth for the ordinary i Flo. 8 -Bracehead. lengths to be uaed. The hole should at starting be larger in diameter than the deeper portions of the boring are intended to be. If the bore-hole is to be deep it is a common practice to dig a small pit, 6 ft. square and 12 to 15 ft. deep, before baring is begun. This small pit is of great utility, an it gives additional clearance for the withdrawal of the rods, removes the loose material at the surface, and reduces the ultimate cost of boring. During the actual operation of boring by percussion, the rods are raised about 1 to IJ ft. and allowed to fall suddenly, driving the chisel against the rook. Every time they are raised the master borer gives them a alight turn with the 'tiller' (fig. 11), causing the chisel to deliver a blow in a fresh direction. When the tool has been at work (or some time the bottom of the hole gets filled with debris, which has to be removed by the sludger, which is screwed for this purpose to the end of the rods. When the ground is soft, and the grindings tine and sandy, a sand pump, working on 16 PRACTICAL COAL-MININO. practically the same principle as an ordinary cylinder pump, is used. If the hole has to be deeper than 20 or 30 yds. a boring trestle and frame are erected; the former as a fulcrum for the brake-staff, and the latter in order to raise the rods easily and speedily when required. In fig. 1 1 are shown some of the tools used in ordinary boring, but there are many others. In boring it is usual to erect some sort of head-gear to enable the rods to be raised quickly and easily. This head-gear may consist of a triangular frame of three long wood poles, either circular or square, meeting at the top, where they are fastened together by a bolt. The head-gear may be from 20 ft. to 60 ft. in length, the higher the better ; but whatever height is adopted, it ought to be a multiple of the lengths of the boring-rods used, so that when the rods are raised, the joint for unscrewing should be just above the top of the bore-hole. Thus, if the rods are in 12 ft. lengths, the boring frame ought to be 24, 36, or 48 ft. high. If the hole is to be a deep one, a steam winch is used, as it raises the rods more speedily, and is more reliable than a hand windlass. When the hole reaches a certain depth the rods require to be balanced in some way, as their whole weight, if allowed to fall on the chisel, would damage or break it. To remedy this, the weight of the rods may be transferred to the end of the brake-staff, or a rope can be used instead, and by a suitable arrangement a weight sufficiently heavy to cut the rock is allowed to fall on the chisel. This plan has been adopted in Mather ott!er Borimj Marhine. — For shallow holes in ordinary strata, such as are generally met with in the coal-measures, hand diamond drills of simple couetruction, and readily transported from place to place, can be obtained at prices varying from £160 to £200, -according to the prevailing prices of diamonds. AdvcaUagu of the Diarnond System. — The advantages claimed for •Tranj. Min. Iiul. Scot.. ISQl, p. 156. 26 PRAC5TICAL COAL-MINING. this system are that it is more expeditious than methods of boring by a chisel, and that, cores of the strata being obtainable, a correct section of the rocks passed through can be ascertained and the inclination of strata seen, while for deep holes it is cheaper than the chisel method. In very soft strata the cores got are not, however, very satisfactory. Davis Calyx Drill — This system of boring, on the rotary principle, closely resembles diamond drilling.* The boring bit, or cutter, consists of a cylindrical metal shell, the lower end of which has been formed, by a process of gulleting, into a series of long sharp teeth. These teeth are set in and out alternately. Those having an outward set are used to drill the hole just large enough to allow the apparatus to descend freely, and the teeth having the inward set dress down the core to such a diameter as to allow the body of the cutter to pass freely over it without binding. The front face of each tooth is perpendicular at the base to the rock to be operated on ; while the back of the tooth rises from the same line at an angle of about 60°. Immediately above the cutter is the core-barrel« which is connected to the boring rods by means of a reducing plug, which also serves to close the lower end of the calyx. The calyx is simply a long tube or series of connected tubes, located above the core- barrel, to which it is equal in diameter. The lower drill rods work through the centre of this calyx, there being an annidar space between the two, and at the upper end the calyx is kept concentric with the drill rods by means of a centering device. Mode of Operation, — When drilling is being carried on, a continuous stream of water is pumped down the drill rods, in the same way as in diamond drilling, the drill at the same time being slowly rotated and forced downward. The rods have to be twisted considerably before they accumulate sufficient energy to overcome the * bite ' of the teeth into the rock, but the moment the surface strain exceeds the resistance below, it begins to grip into the strata by a series of motions similar to that of a stonemason's hammer and chisel action. The debris which is produced by this action in the formation of the core is carried up by the stream of water to the top of the calyx, where, owing to the reduction in velocity of the water flow, they slowly fall back into the annular space between the drill rods and the inside of the calyx tube. It is claimed for this system that a longer core can be produced and more accurate results obtained than with the diamond drill, and that the rate of boring is greater. Other Objects of Boring. — Boring has often to be carried out imderground when old workings, supposed to contain water or gas, arc being approached. In these circumstances, a pair of narrow drifts 6 to 9 ft. wide are driven in advance of the working faces at the nearest point to where the waste is to be tapped. Bore-holes are kept in advance of the face for a distance of not less than 15 ft., and * Trans. Inst, Min, Engt,^ vol. xt. pp. 863-366. THB SEABCH FOB COAL. 27 also sufficient flank holes set at an angle of about 45* with the drift If the coal and roof are ' tender/ and the pressure of the water great, the advance holes will require to extend a good deal further than 15 ft. Whatever length is decided on ought to be adhered to through- out, and the greatest care should be taken, as old plans cannot be implicitly relied on. The holes are usually bored with light iron rods } in. to ^ in. square, and in 6-ft.. lengths, the drill cutting a hole about Ij^ in. diameter, the holes being sloped a little towards the roof. If the old workings take the form of an irregular boundary of * stoop and room,' there is always a danger of an open * drift ' being passed by the exploring road at a short distance from it, so that if the flank holes are not sufficiently close to catch the old roads, the water may break through on the side of the exploring drift, possibly at some distance back from the face. After the waste is tapped, it may be necessary to regulate the escape of water to suit the capacity of the pumping plant, otherwise the pit may become flooded. This is often done by the insertion of a tube in the last length of the hole, into which are fitted wooden plugs, 5 to 8 ft. long, tapered 1 in. to 2^ in., having a hole bored through their centre to allow just as much water to escape as the pumping arrangements can adequately deal with. The tube may also have a tap fixed to it^ when the water can be drawn off as required. If fire-damp is suspected, only safety- lamps should be used, and spare lamps kept ready lighted at some distance in the rear. Precautions should also be taken to provide against other gases escaping in dangerous quantities. In tapping wastes by the ordinary method of drilling holes, over, on an average, 20 ft. in length, there is always much difficulty experienced in getting the tools to clear themselves; indeed, they often get choked up altogether with the loose debris, and occasion much trouble in withdrawal. To remedy this difficulty, boring machines specially adapted for the purpose are sometimes used. Such a machine is shown in fig. 23. The machine consists of a cylinder c \\ in. diameter, furnished with packing glands through which a spindle 8, connected to the boring rods, is worked.* Fixed on the frame is a pump-chest D, which is connected to the cylinder c by means of an india-rubber pipe £ I in. diameter. In this pump-chest are two small plunger pumps, 1 in. diameter and 1 in. stroke. These pumps are worked off two cranks on the spindle 8, and are supplied with water by a pipe leading to a cistern. On the outer end of the spindle is a handle for working the machine. The whole apparatus is placed on a bogie running on ordinary rails. The machine is kept moving forward, while the drilling proceeds by means of a chain fixed to a barrel b with a ratchet wheel ; the chain passes round two other pulleys p p fixed to a prop ^ and a weight W is hung at the other end of the * Trans. Mm, Imt, Scot,, vol xiiL ^ 82. 28 PBACnCAL COAL-BmnNO. chain. The rods, which are Lollow, are | in. diameter outeide with } in. diameter opening, and are made in 6-ft. lengths. Thej are con- nected to each other by the ordinarj' method of screwing. The drill is also hollow and 1} in. outside diameter, and ia of the ordinary description used for drilling holes, except that 1| in. from the point is an opening to allow the water to escape. In applying the machine, the handle is rotated, and this in turn works Uie cranks attached to the two force pumps which force the water into the cylinder c, and thence into the hollow rods, which carry it forward to the drill point, where it is discharged, and flows back through the hole, carry- ing the debris along with it. Holes have been bored with this machine for distances of 150 to 170 ft., the rate of cutting being on an average 30 yds. per shift of eight hours, employing two men. The machine can be used either in ordinary strata or in coal. Fit). 23. —Boring maohine. Old wastes may also be tapped by diamond drills, used in much the same way as when employed at the surface. At the Carron Company's Collieries at Biahopbriggs, near Glasgow, bore-holes were drilled in this manner into old wastes containing water, the distance being about 120 ft. The power was derived from a small Prieetman oil-engine developing 3i horse-power, with a consumption of 3 gallons of oil in eight hours. The speed of the engine was 1 50 to 250 revolu- tions per minute, while that of the drill was 75 to 125 revolutions per minute. The ignition in the cylinder of the engine was obtained by electric spark from a bichromate battery, which served for about 500 hours. The speed of boring in the different strata per shift of eight houra with two men was, in sandstone, 30 ft., shale, 18 ft., ironstone, 15 ft, and coal, 47 ft. Better results coidd have beeu obtained, but the THE SEARCH FOR COAL. 29 position where the drilling was being carried on being confined, short lengths of rods, 18 in., 36 in., and 5i in. long, had to be used at first, which necessitated frequent changing. Other machines used for boring are the Bumside Safety Drilling Machine, ** designed for boring long holes, for tapping flooded workings, and a machine made by Mr Robert Martin, which is really an adap- tation of an ordinary miner's ratchet boring machine, and which can be worked by hand. It has been found most useful in the highly inclined workings of Niddrie Colliery, holes from 50 to 70 ft. in length being bored with no greater difficulty than attends the boring of shot holes. Surveying Bore-holes. — Bore-holes are very apt to depart from the vertical, and may thereby give misleading results; so that it often becomes necessary to ascertain the amount of deviation. This can be measured by the aid of a clinograph or clinostat, an instru- ment which was first invented and used by Mr E. F. Macgeorge in the Colony of Victoria, Australia. It consists of two glass bulbs, the upper one carrying a plummet and the lower one a magnetic needle, both bulbs being filled with liquid gelatine. The needle is so arranged that it can swing freely without touching the sides of the glass bulb, and so set itself in the magnetic meridian. The small glass cylinder, terminating in the bulb at the top. La inserted through an air-tight cork and a brass capsule at the upper end. This upper bulb contains a delicate plummet of glass, with a diminutive hollow float at the top and a solid ball at the bottom, which is prevented from falling out by a delicate grating. It is carefully adjusted to the specific gravity of the solidifying fluid used, and is so arranged that it will assume a vertical position whenever it is free to move.t To use the instrument, six of the bulbs are placed in a bath of warm water, heated nearly to boiling point, and a brass cylinder is also heated by filling it several times with hot water. The clinostats are then put into this cylinder one after the other, and lowered into the bore-hole, where they are allowed to remain for two or three hours. By this time the gelatine will have 'set,' fixing the needle in the direction it had assumed prior to the solidification. The brass cylinder is then withdrawn, and the clinostats are examined one by one in an instrument specially designed for the purpose of ascertain- ing the deviation. Bore-holes may be brought back to the plumb, if deviated, by forcing an india-rubber washer down to a depth of 20 yds. or so beyond the point of deviation, and then nmning in liquid cement to some feet above where the hole has deflected. The cement is allowed to properly harden, when boring may again be commenced in the right direction. * Trans. Inst, Min, Bngs,, voL zxiii. pp. 75-78. t For full description of this instrument, see Mine Surveying^ by Bennett H. Brough, eleventh ^tion, p. 328. CHAPTEB m. SINKING. Frelixniiiary Consideratioiis. — After a coal-field has been sufficiently proved by boring, and the seams have been found to be of good quality and of sufficient thickness to be payable, the sinking of shafts to ' win ' the coal has next to be considered. Sinking operations may be divided into two stages : viz., (1) sinking through the surface deposit ; (2) sinking through the regular strata. The surface deposit is often thin and firm and easily sunk through ; at other times, however, it is the most difficult part of the work. This is particularly the case when a bed of running sand or mud, a thick bed of mud and boulders, or a bed of peat moss, is met with, such formations presenting considerable difficulties to shaft sinking. Before starting to sink, several important points have to be disposed of, among which may be mentioned the following : — The extent of the field or royalty to be worked. The number and thicknesses of seams to be worked. The output to be produced per day to yield a profit on the capital invested. The quantity of water likely to be met with. The number of shafts required, and what their size must be. What their }K»itions should be as regards markets, railway communica- tion, etc. What faults, dykes, or dislocations exist. Size and number of Shafts, — The size and number of shafts re- quired will largely depend on the first two heads : the extent of the field leased, and the number and thickness of seams to be worked. Two shafts are the minimum required under the Coal Mines Regula- tion Act, as a single shaft is only allowed under very exceptional circumstances (see rules 37, 57, 58). The size of the shaft will largely depend on the possible output per day, and on the number of years the coal-field is leased for, or can be exhausted in ; points which may be decided approximately as follows : — (1 ) Tons required to be raised per year = -, I?^L^eBi££l^,t3^ . Number of years m lease (2) Tons reqnired to bo »i«ed per day ='^°»« ^^«^ to bemggd per yew. Number of working days per year 80 SINKING. 31 In England leases are generally for from thirty to ninety-nine years. The number of years for which leases are usually granted in Scotland is twenty, twenty-five, or thirty. The size of the shaft will also largely depend on the depth of the seams from the surface, and the amount of water to be pumped. For an output of 300 tons or less per day, with depth not exceeding 240 yds. and pumps 12 in. diameter, a rectangular shaft 14 f t. x 6 ft. inside the lining would be quite large enough. If circular, a shaft 10 ft. in diameter would suffice, under such conditions. For outputs above 300 tons and up to lOCK) tons per day, a shaft to hold two double cages would be necessary, and this would require increased shaft space. A rectangular shaft 23 ft. 6 in. x 6 ft. 6 in. inside the lining, or a circular shaft 16 or 17 ft. diameter, would, approximately, meet the requirements. Site of Shaft — In choosing a site for shafts, if the surface conditions are suitable, it is generally best^ in the case of a large royalty, to sink as near to the centre of the field as possible, for if this site be chosen, the pits will not be so deep — except where the royalty takes the form of a basin with the deepest part in the centre — as if sunk at the extreme dip ; and the length each ton of coal has to be hauled will also be less. II the amount of water given off in the workings is very large the shafts should be sunk so as to have a larger area to the rise than to the dip, as pumping large quantities of water from dip workings is very expensive. If, on the other hand, the workings be dry, the opposite plan is adopted, as haulage, etc., is usually cheaper from the dip than from the rise, the latter usually necessitating long inclines, which become, in time, difficult and expensive to work. The long side of the shaft is usually simk in the line of the dip of the seam, so as to get the main roads from the pit bottom set off to level course. If the shafts are not sunk in the line of the dip, then to get the road's level course at the pit bottom, the pavement (floor) would require to be cut on one side, while on the other side it would require to be banked up. As a rule it is best to sink the shafts to suit the underground workings, and arrange the surface accordingly. The site should also be chosen advantageously in regard to the transit of coal by road, river, or rail, and close to a supply of good water for boilers, etc. It is a very common custom to sink the shafts close together, so as to concentrate the banking and coal-cleaning arrangements. The landowner sometimes stipulates in leases where they are to be sunk. Form of Shafts, — Shafts may be either rectangular, circular, or elliptical. The rectangular form is almost exclusively used in Scotland and very commonly in America, while in metalliferous mining it is nearly always adopted. Circular shafts are employed in England and Wales for coal-mining, and also on the Continent. In FrBmce, and occasionally in Wales, elliptical shafts are used, and in 32 PBACTICAL COAL-MINING. some parts of Fifeshire, square shafts ; but this form is not to be recommended, especially in the case of large shafts. Each of these forms has its own advantages, the circular being the best adapted to resist heavy pressure, and therefore suitable for deep shafts. This form is also best suited for ventilating purposes, as there is always a certain amount of space imoccupied by the cages. The rectangular form of shaft is more economical to sink, easier lined and secured, and the space can be better utilised for winding, pumping, and other arrangements, while less material requires to be excavated. The author of a paper, read before the Institution of Mining Engineers, in discussing the merits of the different forms of shafts, says, " that in deciding the form of shaft, he fails to understand why in some districts oblong shafts are sunk in preference to circular ones, unless the object is to take out as little ground as possible. It seems desirable, in order to wind a given quantity of coal per day, that there should be the same area (over and above the space occupied by the cage at meetings) in the one shaft as in the other to admit of adequate ventilation. This consideration is in fact so important that in many instances it is deemed desirable to sink a staple pit for a height of some 120 feet, having a holing into the shaft above and below meeting places, so that the area for ventilation may not be diminished when the cages are passing each other. The timbering in an oblong shaft will not last so long as the brickwork in a circular one, and seeing that the shaft is the one entrance into the mine through which all the men must pass in going and coming from their work, it is desirable that it should be made as safe as possible by being securely lined throughout." Commencing Operations. — The position and size of the shaft having been pegged off, the surface soil is removed, the sides being supported with a temporary lining, if required, until the * rock-head ' is reached, when a perfectly level bed is prepared on which to lay the first walling crib. If the shaft has to be lined with brick, the walling may be started forthwith, but very often the sinking is carried on to a considerable depth by the aid of temporary lining, and walled up afterwards. To allow for temporary lining and walling, the diameter of the pit will require to be a good deal larger at starting than the ultimate finished size ; thus a pit intended to be 15 ft. diameter inside the walling should be begun with a diameter of 17 or 17 J ft. at least. The curbs that are used are generally made of oak, cut into segments to fit the circumference of the shaft, when the latter is circular. They vary in size, being commonly 6 in. x 4 in. or 9 in. x 4 in., while sometimes they are made 6 in. square. The segments are dressed and fitted together at the surface, and are then sent down the pit and jointed together by cleats. Figs. 24 and 25 show the construction of some of these oak curbs. Where the shaft has to be supported with temporary lining, a siHKiHa. 33 sqiiftre frame made of four strong oak beams, 12 in. to 16 in. square, and Srmlj bolted together, is laid across the top of the pit, and to this the wood lining is secured. Figs. 26 and 27 show how this temporarj lining is fixed in the shaft. When a curb is placed in position, ' backing deals ' or ' lagging ' of white pine boards, 6 to 9 ft. long by 9 in. to 12 in. broad, and 1^ in. or 2 in. thick, are fitted in all round between the sides of the shaft and the curb. When these are fixed, other curbs are put in, about every 6 ft., until the surface is reacheid, and are kept in position by ' punoh props ' inserted between them, all round the shaft ; and finally they are secured to the cross- beams at the surface by means of 'stringing deals,' which are also carried down from curb to curb as the work proceeds (fig. 35). If P»a- m. lagging dtmla b'stringinq dttlt cpuneh propa Fios. 28 and 27.— Tempowry lining. this temporary lining continues to any great depth, its weight may be transferred to other beams fixed in the shaft. It has now become the custom to discard the use of wooden curbs, and to substitute iron skeleton rings iu order to keep the temporaij lining in the shaft. Behind these rings are placed the lagging, or backing deals, which consist of planking 2 to 3 in. thick. The iron rings are easier to handle and put together than wooden curbs. 34 PRACTICAL COAI^UtHlKG. When the walling of maHonry is about to be commenced, the sh&ft is 'laid back' for 2 ft. or 3 ft., and an even bed prepared for a walling crib ; the crib being carefully laid, the walling proceeds, and is carried up for a distance of 10 to 15 yds., when another crib is placed in position. These cribs are now made of cast iron, oast in segments to suit the circumference of the shaft. When the stmta are bard and strong, and a section of brickwork is to be put in, no crib need be used ; the walling is simply started direct off the rock, and carried up in the usual way. A satisfactory method of proceeding is to carry sinking on for part of the week, and walling operations for the rest of the time. The method of sinking and walling simul- taneously is described later. In starting to sink below the walling, the shaft is cut narrow at first, and gradually widened out to its proper width, so as to leave a ledge of rock to support the walling Fio. 28.— Diagram of Buildng. Fio. 29.— Huging Kaffold. above (see fig. 28). When, at a later stage, the walling is being built up from below, this ledge is not removed all at once, but it ia taken out in sections around the circumference, these sections or arcs being then built up to the walling above until the junction is made good all round. The masonry is not usually built back close to the strata, but a small space is left, which is filled with fine ashes or other porous material, so that it helps to relieve the pressure arising from the sides on the brickwork. The walling is carried on by means of a ' hanging scaffold ' or ' walling cradle,' made up of 3-in. or 4-in. planking, bolted together and made to fit the curve of the shaft. It is usually made with lin. or 2-in. clearance all round, and guides the workman in the building of the brickwork. The 'cradle' is secured to the winding rope by four chains, the latter being fastened to the scaffold by eye-bolts (see fig. 29). The scaffold should be made to fold up at the centre, so that when a section of walling la completed it can be folded and slung to the sides of the shaft, instead of being raised and lowered each time. Sometimes the walling is carried out by the help of iron sections, fixed all round the outeide circumference of the walling scaffold. The height of these sections is from 2 ft. to 3 ft. 3 in. The brick- work is placed around and in contact with it. When a circular tier of walling is thus completed, the iron section is raised and another tier of masonry placed in position. In this way the time usually spent in measuring the diameter and ascertaining whether the masonry is vertical b saved. When the space between the walling and the strata is to be filled Fina SOiDd 31.— GallowB.7'BseaGr the men working at the pit-bottom. When the strata passed through are soft and unable to bear the veight of the curb and walling, holes are drilled all round the side of the pit, and strong iron rods I^ in. to 2 in. diameter and 1^ to 3 ft. long, on which the crib is laid, are driven in. The walling then pro- ceeds in the usual way. When these rods require to be used, the distance between the curbs should be very much shorter than in bard strata. When the strata are giving off water, ring curbs will require to be put in, to protect the brickwork and to convey the water to a lodg- ment in the shaft, which is done by having a pipe connection between every two curbs. The ordinary ' garland ' or ' water ring ' is usually an iron curb, cast with a groove, and is often a walling and water curb combined ; sometimes it *'*' is made of wood and an annular space left in it. Above each curb the brickwork is ' shorn ' back to allow the water free acoess to the ring (see Gg. 34). It is most impor- "■*'■'' tant that these rings should be thoroughly water-tight. Sometimes a layer of well- puddled clay is put m behind, but a better plan is to lay them on felt or oakum, and Fio. 8#.-Walerrii.g. grout them with good cement. In walling, a good quality of brick is most necessary, the moat satisfactory l>eing good alumina tire-bricks. Except in very small shafts, ordinary shaped bricks can be used ; the mortar employed should be made from good hydraulic lime, miied with 'mine dust' from calcined iron-ore heaps, which makes a better binding material than sand. The general arrangement of the walling, guides, etc., of a circular shaft 12 ft. diameter is shown in figs. 35 and 36, the shaft being fitted with wood guides. Tubbing. — When large quantities of water are met with in the strata to be sunk through, cast iron tubbing is used to keep back the inflow, to save pumping and keep the shaft dry. The tubbing (figs. 37, 38, 39) is made in segments suitable to the radius of the pit, the depth and thickness of each segment varying according to the pree- sure to which it is to be subjected. The rings or segments are built up from a ' wedging curb,' carefully laid on a smooth bed out round the pit. The wedging curb is a box-shaped ring of cast iron I in. to 1^ in. thick, 6 in. to B in, deep, aad 12 in. to 14 in. wide, and made in convenient seotiona. At the point where a. wedging curb is to be placed, the shaft is ' ahom ' back to admit ita being placed in poeitioD, and a small annular space is left all round. When the curb has been laid in position and securely wedged, the tubbing is built up from it, the joints between every two rings of tubbing being filled Fios. 3f> kod 36.— Plan snd eectiunal elevation of oirculiir Bhaft. with soft fir sheathing or thin sheet lead so as to secure a water-tight joint. The spaces left between the tubbing and the strata are usually filled with good concrete or cement. The segments of tubbing are gaoeially cast smooth on one side, and a small hole left in the centre to relieve the pressure of water behind, while it is being built up, these holes being afterwards carefully plugged up. A corrugated 40 PRACTICAL COAL-MINING. form of cast-iron tubbing has been employed on the Continent with excellent results, as it is both strong and light. The thickness of Xtevo'ttfin' o£ ^ei/C'k irnr Fios. 37, 38, and SO. —Segment of tubbing. tubbing required will vary according to depth and pressure to be resisted. The thickness may be found from the following rule : — <= -^1 where t= thickness of tabbing in inches. R= radius of pit in inches. p= pressure per sq. in. in lbs. =head in ft. x *434. M = factor of safety (6 to 10). /= resistance of tubbing to crushing. (For cast iron /= 100,000 lbs. per sq. in.) Kxample. — What thickness of the tubbing would be required for a shaft 15 ft. diameter, and a head of water 50 fms. ? t^ 90 X 50 X 6 X '434 x 10 100,000 = ri7 in. +^ in. (to allow for wear). N,B. — This would be the thickness required at bottom of tubbing. The formula given by Greenwell* will also supply the same information. 50,000 Where x =» thickness of tubbing in decimals of a foot ; P » depth in feet ; D »= diameter of pit in feet ; '03 = a constant. • Mint Engineering^ by C. Greenwell. SINKIHG. 41 Common of Tubbing. — Certain BubBtanoes held in solution by WRter are very injurious to iron surfaces, and to prevent corrosion, the tubbing often receives a coating of tar or of some hard vamiah. In up-cast shafts where furnaces are used for ventilation, the fumes and gases given ofF by the furnace are also very injurious, and the only remedy is to line the tubing with good fire-brick to protect it. Coffering. — Another method of shutting off water from the shaft b to use coffering, which is simply a brick wall with a space in the centre, this space being filled in with good cement, which makes a water-tight walling. A third method of coffering differs some- what from that usually employed. The wall in this case (fig. 40) is of 4} in. brick- work, about 3 ft. at a time being built, while Id front were placed sheet-iron plates a <■ 14 to 16 wire gauge.* In front of this, brickwork 20 in. thick was built up, leav- ing a space of 11 in. between the inner and outer walls, to be filled in with cement, in which the iron plates were also embedded. As the pressure of the water became less the thickness of the walling was gradually i reduced from 20 in. to 16 in., and finally to 10 in., the space for cement being kept in continuous lengths. The beet results are obtained when the water in the pit is allowed to follow the work, so that the cement sets under water, but this is not always prac- ticable. The brickwork in the walling should also be set in cement. At the bottom of the wat«r-bearing strata a short length of solid walling should be put in wherever possible, and the water conveyed through it by pipes. It is generally found that when water is met with, a considerable quantity ^tpv'' percolates through the brickwork for a few _ days, but as a rule it ultimately becomes pio, 40.— Coffering. quite dry. The cost of coffering of this deecription was, in a particular instance, £6, 6s. 8d. per vertical foot over a distance of 240 ft., which included the cost of labour aud material, and the exact cost of enlarging the shaft sufficiently to admit of the extra thickness of walling. The cost for tubbing of the same length was estimated at X12 per foot for a shaft 18 ft. diameter. But £12 per foot is a very low estimate compared with some instances where this method has been adopted; as, for I, at Shireoaks Colliery, where a total depth of 170 yds. • JVbhi. Fm. In*. Uin. Rtgit., vul, viii. l.l>. 18, 19. 42 PRACTICAL COAL-MININO. of tubbing jn a shaft 12 ft. diameter cost no less than £60, 2s. per yard. During the sinking of the shafts at the Maypole Colliery great difficulties were experienced from extensive water feeders, one of which delivered 90,000 gallons of water per hour. The coffering arrangements, which were of a complicated and costly nature, have been described in detail in the Journal of the British Society of Mining Students* The thickness of coffering required to resist a given pressure of water can be found by means of the formula given in the case of tubbing, except that a different value must be assigned to/, viz., the crushing strength of good brickwork set in cement, which may be taken as about 2500 lbs. per sq. in. Cost of Sinking, — This will depend on the nature of the strata to be sunk through, the quantity of water to be dealt with during sinking, the size of the shaft, and the price of labour. In the particular districts labour will probably cost from 6s. to Ids. per cubic yard excavated. The cost of sinking and lining the two shafts at Harris's Navigation Colliery, each 17 ft. diameter, was as follows t : — Average cost per yard for sinking 50 yds. in shale near pit bottom. Without Pumps. With Pumps. Labour,. . . £9 8 2 per yd. £10 2 4 per yd. Material (Stores, etc), . 2 11 4 .. 3 0 4 Total, . £11 19 6 ti It £13 2 6 >t !♦ In hard rock the cost was £44, 13s. 2d. per yard, using pumps, and the cost for walling in the same shafts, for 18 in. brickwork and two curbs per yard, was J&ll, 7s. lOd., or an average of £1, Ss. lOd. per cubic yard of brickwork, which seems rather high. To the above cost would require to be added the cost of guides and fixing, which would be about 25s. per yard, if iron or steel guides are used ; if wire rope guides, the cost would be 10s. to 12s. 6d. per yard. The cost of sinking a shaft 20 ft. in diameter, 600 yds. deep, with 18 in. brickwork, in a Webh colliery, has been given by Professor Galloway as follows : — Wages and salaries, £14,400, . 2,500,000 bricks @ 85s. per 1000, 950 tons of lime ® 10s. 6d. per ton, 3500 tons of sand @ 5s. 600 tons of coal @ 6s. Timber for mid-brattice, etc., Stores, lighting, etc., . Contingencies, . If »* ti II . £14,400 4,876 498 875 180 1,000 8,000 8,000 £27,828 * Vol. xxi. p. 65. t 7'rans, Innt. Civil Engs,^ vol. Ixiv. p. 23. SINKING. 43 This gives an average of £46, lOs. 4(1. per yard for sinking and walling alone. The rate of sinking averaged 8*3 yds. per week, and 3000 to 4000 gallons of water per hour had to be dealt with. Bate of Sinking. — This varies very much according to the strata and difficulties met with, ranging, for a shaft 15 ft. to 16 ft. diameter, from 2^ to 3 yds. in very bard strata to 8 or 10 yds. in ordinary strata per week. Sinking Bectangular Shafts. — The procedure is much the same in sinking rectangular shafts as in the sinking of circular ones. The shaft having been properly pegged off, the surface soil is excavated, as already described, and the sides supported with temporary wood, until a convenient depth or the rock heisul is reached, when the first set of * barring ' is usually put in, great care being taken to square the bed for it, and to set it level. The first set having been properly adjusted, others are built up above it, to 3 ft. or there- abouts above the surface, to afford sufficient height for emptying the material excavated, and also to prevent water flowing into the shaft. Racking Fios. 41, 42, aud 48. — Fixing timber. the back of the barring being well puddled with good blue clay for this purpose. The sets of barring are fitted into the shaft, either cut square, with an ordinary ^butt' joint, and comer trackings (fig. 41) put in to bind them together ; or they may be notched into each other (fig. 42), which makes a neater and stronger job. Comer rackings are also used square as at fig. 42, and angle-bars are also occasionally employed for this purpose (see fig. 43). They are neat and strong ; and they have the further merit of lasting very much longer than wood. The barring when put in position should be well and tightly wedged at the comers, and also opposite each bimton; the spaces behind the barring should be well packed with some light material, branches of fir trees for preference, to ensure efficient drainage. Figs. 44 and 45 show the plan and elevation of a rectangular shaft, and illustrate how the lining, buntons, etc., are fixed. The sizes of wood used for barring (lining) vary according to the nature of the strata passed through. In ordinary strata not giving off much water, barring of white or red pine, 9 in. x 4 in., is used at the surface, and 9 in. X 3 in. in the rest of the shaft. Where the pressure is great and the shaft large, or where loose material has to be passed through, the baning may be 9 m. x 5 in. or 12 in. x 6 in. The comer rackings 44 PRACTICAL COAL-MTNINa. are UBuallj 2} in. x H in. or 2 in. square ; if angle iron is imed it may be 5 in. x 5 in, x J in., or 5 in. x 4 in, x ^ in. Wood lining in dawn-cast shafte lasts, on an average, about fifteen years, but in up-caat shafts the average is much shorter. When the barring is fitted in it is further strengthened by wall- plates and huntons, the former being put opposite each bunton, and the latter themselves being put in at right angles to the barring, the perpendicular distance between them varying from 3 ft. to 6 ft., according to the strata passed through, but averaging 4 ft. The Kioe, 44 and 45. — Plan atid elev&tioD of rectangulu- ahaTt. buntons may be of either white or red pine ; the sizes used are 5 in. X 5 in., 6 in. X 6 in., or 8 in. x 6 in., or for small shafts 8 in. x 3 in. It is now the general practice, especially in large shafts, to put ' fiUing-in pieces ' or ' pmich props ' between the buntons at each end, and also at the centre of each of the latter, these 'punch props ' giving greater strength and stability. Rectangular shafts are now generally lined from top to bottom. This gives additional security to the shaft, aud facilitates the fixing of the buntons and guides. After the surface soil has been sunk through it is usual t« er«ct a siNEn^G. 45 windlass or steam crane, but a windlass is only suitable for small shafts, and can only be economically used for depths of 15 or 20 yds., beyond which it is better either to employ a small temporary sinking engine, or to erect the permanent winding engines at once. For large shafts steam cranes are much used for the earlier sinking, as they give more power than a windlass, besides being speedier and safer to work with, while the bucket can be swung clear of the shaft, and landed at any desired point for tipping. If a temporary engine is used for sinking, it should be placed in such a position as not to interfere with the erection of the permanent winding engine, otherwise much delay may be caused. The temporary engine is often erected as close to the shaft as possible, so that the permanent engines may be laid down behind it, and the erection of screens, etc., may be proceeded with while sinking is going on. This saves time and enables coal to be dealt with immediately the shafts are sunk. The sinking engine is sometimes placed in such a position that it can be afterwards used for haulage purposes under- ground. When sinking, the shaft is usually covered over, only sufficient space being left for the bucket to pass through. When the kibble is tipped at the top of the shaft without the aid of scaffolding, a strong beam is laid across the pit, to which * sliding^ deals are fixed, to prevent the bucket from catching the mouth of the shaft, and also to make it ' strike ' easier if no bogie or chain is used. Very often a bogie is used for receiving the kibble when it arrives at the surface, made so that it entirely covers the shaft (fig. 46), and prevents anything from falling on the men at work at the bottom. Some- times a chain or rope fixed to a beam on the pithead frame is used to swing the kibble clear of the shaft. Another method of closing the top of the shaft is by means of folding-doors with rails on their upper sides. The accompanying illustrations (figs. 47 and 48) show the arrangement used by Professor Wm. Galloway while sinking the Llanbradach shafts.* The two folding wooden doors are held together by hinges d a', which are keyed on to shafts h V, Balance weights, c c c c', are attached (two to each door), and these are connected by rods dd\ through cranks on the two opposite shafts so that the doors open and shut simultaneously when the hand lever g is drawn backward or pushed forward respectively; ee' shows the position of doors when open, and the balance weights//* will then be in the position shown in fig. 47. If the doors are shut when the winding rope is in the shaft, the two guide ropes and the winding rope pass through three holes on the centre line of the door. A beam is put across the shaft directly below the balance weights, which are boxed in to prevent the possibility of any accident. The rods, levers, cranks, and balance weights are also boxed in above, and only the lever g projects through longitudinal slots in the cover. In using • Lectures on Shaft Sinkingt p. 7. 46 FBACTICAL COAL-HINIHO. tbia apparatus, when the hucket ie at the surface, the doors are closed, luid a tipping wag^n into which the contents of the bucket are emptied is run on, without taking the bucket off the winding rope. The waggon is then withdrawn, the doors opened, and the bucket is ready to descend. Whatever method is adopted, great care must be taken to let no loose material, such as stones, bolts, etc., fall down the shafts. Preparing Ihe iVooil. — All wood, such as barring, buntons, racking, etc., should be prepared at the surface, ready to be sent down the pit ea required, as this saves much labour, wood being difficult to cut and dresa in a confined shaft. A band winch, with a thin wire rope Fio. 46. — Amngemsnt for receiviiig kibble with bogie. and a large muzzle attached, should be kept ready for lowering the wood to the sinkers as required. Dupositiou of Lalxjar ami Tooh Required. — The sinking is gener- ally carried on continuously during the twenty-four hours, with the exception of Sundays, and the number of men employed on each shift varies according to the size of the shaft, etc. For a rectangular shaft 23 ft. X 7 ft. the number of men employed would be twenty- one, i.t. seven men on each shift ; for smaller shafts three or four men on each shift would be sufKcient. In a circular shaft 18 ft. bo 20 ft. in diameter, sixteen to twenty men should suffice for each shift ; an average labour allowance being one man for every 18 to 20 square feet of sinking. SIHEIKO. 47 The tools used in aiDking are spades, shovela, picks, jiiDipere, 2 ft., 3 ft., and 4 ft. loo)!:, and 1 in. to 2 j in. acroas the mouth ; single and double-headed hammers, stemmera, cleaners, saws, axes, screw- keys, and porting-boltB. Two kibbles will also be required, each to tios. 47 uid 48.— G1JI0WI17 »j»t4ao. hold 10 to 20 cwta. of material, and also a water-barrel to hold 15 to 30 cwte. of water. Special Methods of SinkiDg. — When thick beds of running sand, gravel and water, or peat moss or mud and boulders, are met with either at the surface or further down, the following special methods of sinking may be employed ; — Sinking b; pil« driving. Sinking by brick drum, iron or Bt«el cylinders, recUnguIar iron cjlindara. Sinking bj cotnbiBslion of brick drum and iron or steel cylinder. Sinking t^ compreEsed sir ; e.g., Triger BTstem. Sinking bj boring or drilling uut the shaft ; e.g., Kiod-Chaadron sjsteni. Sinking b; freezing the itrvts ; e.g., Poetsch or Gobert systems. PUe^riving, or sinking by piles, is one of the commonest and easiest methods of sinking through a moderately deep bed of sand met with at the surface. 48 PRACTICAL COAL-MINING. The piles used for this piirpoBB are usually of red or white june 12 to 15 ft. long, 9 in. bruad, and 3 in. thick, sharpened and diod with iron at the bottom, to facilitate driving, while at the top a hoop of iron is shrunk on to prevent splitting while the pile ia being driven down {see fig. 49). Before starting to sink, a strong frame- work of timber, of the size required, is fitted together, and laid down on the site where the shaft ia to be sunk. The first set of piles are then driven in all round it 'skin for skin,' the commonest method of driving them being by hand, the man using a large mallet. If they cannot be driven easily by the mallet or hammer, a ' monkey ' may be used, or the necessary pressure applied by means of a hydraulic ram. As the piles of each succeeding set are driven in they are firmly supported by aide and end bars, and buntons placed at convenient distance apart, aa shown in fig. 49. When a pit has to be sunk by this method, it must be commenced very much larger than the finished dimensions required, especially if the depth of sand to he sunk through is considerable, as every set of piles put in reduces the size of the shaft by at least 18 in. Sometimes the piles are driven inclined outwards to keep the size of shaft from being reduced too much, but by this method it is more difficult to keep the barring perpendicular. If any space is left between the piles and the walling or barring, it should he filled up with good cement or concrete, and the piles withdrawn if possible. Sinking by piles ia an expensive method, and some- times not a very successful one, if the aand Fio. 18. —Pile-driving, IB very quick, or when the strata are watery and mixed with boulders. The limitof depth that can be sunk through by pile-driving is about GO or 70 ft., but it is more efficient when the depth does not exceed 30 to 40 ft. Brick Drums. — Sinking through running sand is often done by what ia known aa the ' Dnim ' method. When this systom is adopted, a curb of wood, 14 in. to IS in. broad and 6 in. thick (figs. 50, 51), ia laid down on the site to be smpany in the north of France, the shaft was bored out in two operations ; a first pit 6 ft. 6 in. wide being sunk to a depth of 10 or 12 yds. beyond the watery strata, which was subsequently enlarged by a second boring to the full size.* On reaching the required depth the teeth of the trepan are set 80 as to cut a horizontal and level bed for the tubbing to rest on, and the use of moss-box, equilibrium tube, and false bottom can be entirely discarded. Work can, by this method, be carried on with great rapidity; in one instance the small shaft was bored out to a depth of 366 ft. in seventy-five days, the larger one being bored out to 327 ft. in four months twenty-one days, and fixing the tubbing occupied two months longer. The ordinary rate of boring by this system is 9 to 12 in. per day, according to the depth and diameter of the shaft. Lippman's Method. — This method of sinking is practically the same as the Kind-Chaudron, but instead of the shaft being bored out in two or three operations, it is completed in one, i,e. the shaft is bored out from the commencement with a large trepan specially made for the purpose. AdTantages of these Systems. — For this and the Eind-Chaudron method of sinking the advantages are t : — The use of pomps is avoided, unless when the shaft requires to be cleared after the tubbing has been lowered. The risk of accidents to workmen, which are common in the ordinary mode of sinking, are reduced. The inconvenience of draining the surrounding springs, which in a populous district depending on these for a water supply would be g^reat, IS avoided. Shafts may be sunk to coal seams through ground which it would be impossible to deal with by the ordinary methods of sinking. Against these advantages there must, however, be set the fact that these methods of sinking are very costly. The cost of such sinkings may vary from £50 to £150 per yard depth, according to the strata and the difficulties encountered. This price does not^ of course, include the cost of the tubbing and other accessories. Pattberg System. — This system, like the Kind-Chaudron, is applied for drilling out shafts in water-bearing strata containing hirge quantities of water. It somewhat resembles the Rind-Chaudron method, but has several distinctive features which are quite new. * Ore and Stone Mining, sixth edition, p. 293. t Tran$. Min. Inst, Scot,, vol. vi. p. 28. 60 PRACTICAL COAL-MINING. Two shafts have recently been successfully sunk by this method at the Rheinpreussen Colliery, near Homberg, Germany. The principal appliances used in this method of sinking are the percussive boring tool mounted on a strong wooden or wrought- iron frame, and supported by a tubular boring rod (see figs. 66, 67), and two mammoth pumps, the whole being slung from a scaffolding over the shaft, and an oscillating drum, driven by a steam engine, for giving reciprocating motion to the cutter. The borer B (fig. 67) hangs on a wrought-iron tubular boring rod, having an inside diameter of 150 mm. (6 in.) and 15 mm. (f in.) thickness of metal. The chisel-carrying part r is also of wrought iron. It slopes upwards from the centre to both sides, so as to cut a surface inclining towards the centre of the shafts, and has on either side a tube-like piece a, from which the small channels bb branch off at Fio. 66. — Pattberg System. right angles and lead into the corresponding channels in the steel chisel teeth zz. The tubidar boring rod, from which the cutting tool is suspended, is in communication with the hollow pieces (a a), and supplies the water which flows out at the edge of the chisel teeth. The vertical and horizontal guiding arms u and v, as well as the other supporting pieces, are made of wood. The apparatus which was first employed had a cutting edge of 6*4 metres (20*99 ft.) broad and 8*3 metres (26*89 ft.) high in the centre, the total weight of the boring piece being 19,800 lbs. Instead of the screws hitherto used for holding the individual parts together, wedges were used for this new borer, as it was thought that owing to the large nmnber of times it had to be raised and lowered, the screws would very soon become loose* Further, instead of constructing this borer with teeth, a straight cutting edge was put on. BiHEma 61 At either side of the tubular boring rods is one mammoth pump. These mammoth pumps consist of two pipes (R R, fig. 67) of 3 mm. ('117 in.) and 140 mm. (6 5 in.) inside diameter. The pipes reach down almost to the point of the borer, and enclose a second pipe of the same thickness and 100 mm. (3'9 in.) diameter. In the annular space between the two pipes compressed air is brought from the surface, which is allowed to escape a httle above the lower end into the inner tube. This lauses a pressure on the surface of the detrital sludge, causing it to be suclced off the centre of the shaft and brought to the surface. The tubular boring rods are led into the shaft scaffolding through a hollow guide, and have on the top a revolving piece to which a rope is fastened. This rope is wound round an oscillating drum ((, fig. 66), which is operated by a steam engine through a crank sh^t /' connected to a large drum or disc N. In order to release the boring arrangement the weight hanging on the rope is partly adjusted or counterbalanced by steam pressure, by means of a pliwger, connected by a rod <7 to the drum N. About 40 horse-power are required for starting the boring arrangement. While boring is proceed- ing, the alternate slacken- ing and tightening of the rope, to give percussion action to the cutting head, p,^ 87._p»ttbcrg Cutter. b effected in the following manner : — The drum (fig. 66) revolves on the axle e of the boring aoparatus, drum t and another disc behind 1 are fixed to the axles by wedges. The disc behind holds a circular rack {i.e. a rod with teeth on it) into which the spur-wheela dd catch. From a pulley also revolving on the axle e these spur-wheels are driven by smaller spur- wheels n II. The belt connecting the pulley with another one fixed on the axle of the disc e is, as a rule, slack. When it is made tight the teeth wheels dd are caused to revolve, and set the boring apparatus in motion. For the purpose of changing the position of the cutting tool at the bottom of the shaft, a ' Kriickel ' (tiller) is fitted on to the boring rods at the surface, and is operated in 62 PRACTICAL COAL-MINING. exactly the same way as when small bore-holes are being put down by the ordinary percussive method. For the lowering and taking out of the borer and piunps a steam crab is used, which is set up opposite the boring appliance, on the other side of the shaft scaffolding. The total weight of the tubular rods and the necessary pipes amounts to 297 lbs. per current metre (3*28 ft.). The cutting head is worked at the rate of fifty to sixty strokes per minute while boring goes on, the height to which the cutter is lifted being 18 to 20 cms. (7 to 8 in.). At every round the borer is set in afresh twenty to sixty times per minute according to the resistance offered by the ground. About fifty men are required in connection with this work. They are spread over three shifts of eight hours each. In every shift four men are employed on the boring stand. In the deepening of Shaft IV. at the Rheinpreussen Colliery a sink- ing wall of 8*90 metres (29*19 ft.) clear diameter was built. The boring of the loose ground was then effected by means of a breaking appliance driven by hand labour. When the wall had been sunk through a layer of gravel of a depth of about 17 metres (56 ft.), the sinking working was temporarily suspended and the bottom of the shaft was filled up with concrete for a depth of 10 ft. After giving this concrete three months' time to become hard, a new sinking cylinder of 6*5 metres (21*32 ft.) diameter was built in and the sinking resumed, the percussive drill being used to penetrate through the concrete, which was cut at the rate of 4 ft. per day. This method of sinking has up till the present only been applied to loose wateivbearing strata, and it has yet to be demonstrated that it would be equally successful in hard ground; but in view of the satisfactory results obtained in boring through the concrete layer, this does not appear to be out of the question. Gobert*B Freezing Method. — In the Poetsch freezing system, when any great depth is reached, the pressure of the liquid within the tubes becomes very high, and frequently brings about leakage of the liquid into the surrounding strata, which renders it impossible to freeze them effectually. In order to obviate this difficulty Gobert uses a cold transmitter, the pressure of which is lower than that of the water outside the tubes, while anhydrous ammonia vapour is used instead of the freezing liquid in Poetsch's system. With ammonia vapour very low pressures can be maintained, even at great depths, and if the tubes are not water-tight, instead of ammonia leaking out, the water from the surrounding strata would force its way in, and a coating of ice would be formed on the inside of the tubes, which would check the further inflow of water. In order to vaporize the liquid ammonia in the tubes, these have to be connected with a suction and force pump. This pump sucks in the gas and compresses it into a liquid, with the help of a con- denser, and then forces it into the freezing tubes. In order to avoid snnnNO. od the fall of the liquid to the bottom of the freezing tube, aad to vaporize as much of it as possible in a given unit of time, the injector is made of a form spiral in one plane (see figs. 68, 69). The liquid, the entrance of which into the injector is carefullf regulated, falla slowl; in a thin stream within this spiral tube, and meets on its way a series of small orifices placed at various intervals in the tube. By these orifices the liquid escapes into the freezing tube, and vaporizes. In the Poetsch system the watery strata must be all frozen from tlie bottom upwards before the sinking can be proceded with, but by Gobert's method the strata are frozen from the top downwards, thus allowing sinking operations to be . started much sooner. Simul- initt taneously with the sinking opera- tions, fresh strata can be suc- cessively frozen, and so allow of continuous sinking. Freezing of the strata can bo carried to great depths by this system; Gobert states that strata at a depth of 3000 ft. from the sur- face can be dealt with. For a recent sinking the cost of this system was £40 per foot. Koch'8 Freesing SyBtem.— This system resembles that of Gobert's, but gaseous carbonic acid, ammonia, or a mixture of sulphur dioxide, is used as the refrigerating agent. Anhydrous ammonia, which has a density of 0'59, taking air as l,and boils at — 40° C. at atmospheric pres- sure, is generally us«i. At the Washington Colliery, Durham, dog. ss «nd 69.— Gobart's freering tuba. where the first two shafts sunk by this system in Britain were bored, the evolving brine used was a iolution of 26 per cent, of magnesium chloride dissolved in hot water, which freezes at a temperature of - 34* C. The refrigerating agent is first subjected to a pressure of 150 lbs. per sq. in. by two com- pressors, and then delivered into a small receiver, from which it passes to the condensers, through a pipe 3 in. diameter, and thence into four tubes, each 1 in, diameter. These condensers are vertical iron cylinders, 10 ft. high and 5J ft- in diameter, and contain, in tiers of four rings, 1600 ft. of tubing, 1 In. diameter, through which the ammonia circulates. About 4000 gallons of water per hour circulate through the condensers, the water being kept in constant motion by lueauB of paddles, Tbi^ cools the ammonia, reducing it to a li^^uid. 64 PRACTICAL COAL-MINING. The condensers are connected to the refrigerators by piping 1 in. diameter, the refrigerators, like the condensers, being vertical iron cylinders, 10 ft. high and 7 ft. in diameter. These refrigerators, of which there are three, are jacketed first with 3 in. of peat-moss and then encased with wood. They are filled with the brine, and contain about 2000 ft. of tubing 1 in. diameter, through which the ammonia circulates after passing through reducing yalves, which has the effect of reducing the pressure from 150 lbs. to about 15 lbs. per sq. in. At this point the ammonia is immediately changed from the liquid to the gaseous state, and as this can only be done by absorption of heat corresponding to the latent heat of vaporization, this heat is taken from the surrounding bath of brine, which is thereby greatly reduced in temperature. At the Washington Colliery, before commenc- ing the freezing process, the top of the shaft was enclosed, and the exposed pipes covered with straw. A hole was bored, and a pipe 18 ft. long inserted in the middle of the shaft, and the height and temperature of the water in the hole was noted as the gradual increase of ice-wall slowly caused the water to rise. FoetBch's Method. — In this system of sink- ing, watery strata is artificially solidified by freezing. A series of bore-holes are first put down in the area where the shaft is to be sunk, and these are then lined with tubing through which a freezing solution of chloride of calcium is made to circulate by means of pumps. The freezing mixture, which is at a very low tem- perature, absorbs heat from the surrounding watery strata, which freeze into a solid mass, when the excavation of the shaft can be carried on in the ordinary way. Fig. 70 gives a sketch of the freezing pipes which are inserted into the bore-holes. They consist of an outer and inner tube, the freezing liquid being forced down the smaller inner tube circulating round the outer one, and escaping at the top, where it is led back to the refrigerating machine and used over again. The large tubes, which are 6 in. to 8 in. diameter, are plugged up at the bottom with lead, cement, or any other substance that will render them water-tight; great care being taken to make this stopping secure, as the success of the operation practically depends on this precaution. The number of tubes required will depend on the strata and the difficulty or otherwise of solidification. At a pit sunk at Lens in the north of France by this method, the area frozen was about 40 ft. diameter aqd 137| ft. deep, the number Qf tubes u^ was 28, an(} Fio. 70. — Freezing pipe. SINKINQ. 65 the freeziDg of the strata took about 120 dap. Figs. 71, 72 show the general arrangement of the tubes in the shaft. In this system there is considerable risk of failure ; for should there be any leakage or improper plugging of the tubes, the freezing mixture, which is iteeH uncongealable, may escape, and by permeating the strata render attempts to freeze the water futile. The freezing mixture or brine is usually a 20 per cent, solution of calcium chloride in water. It is cooled by means of ammonia, circulating in coils, at a pressure of 9 atmospheres (135 lbs. per sq. in.), in a liquid state. The temperature of the coils is 20 to 22° C. below zero, and FiOB. 71 and 72, the brine leaves the cistern at a temperature of about - 12° C. and returns to it at - 9° C. AcceesorieB to Shaft Sintiiig— The operation of raismg the excavated material during sinking is usually done by kibbles or buckets, which may be made either of iron or wood. The best form of sinking kibble is that in which the arms are fixed on trunnions with a catch at the top. Fig. 73 illustrates this kind of kibble. The gT«at advantage of using one of this sort is that it can be completely and easily emptied without requiring to be detached from the winding rope, or even lowered on to a scaffold, for if it be swung clear of the shaft it can readily be emptied at any desired point by knocking up the catch a, which releases the arms and allows the body of the bucket to revolve on the trunnions b h. Sometimes kibbles constructed of wood and bound with iron are used instead of iron ones, but they a.Te not so handy nor yet so durable as those made of iron. Fig. 74 66 PRACTICAL COAL-MINING. shows a wood kibble which is well adapted for raising water and ordinary material. Before the kibble is raised from the bottom of the pit, the sinker in charge ought to examine it to see that the fastenings are secure, and that no stones are likely to fall off, or that none are sticking to the outside of the kibble, liable to be knocked off during the ascent of the kibble, and possibly injure those who are working in the shaft. The same precautions should be adopted at the surface when the kibble is being lowered into the pit. Safety Riders, — In the majority of shafts in process of sinking, the kibble is raised without being guided in any way; the Fio. 78.— Iron kibble. mwxjamuumtMmm Fio. 74. — Wooden kibble. common method being for the engineman to raise it a few feet from the pit-bottom when it is filled, and it is steadied for a few moments by one of the sinkers, and then drawn right away to the surface. This method acts very well if there is plenty of space in the shaft, and the depth not great ; but when the depth becomes considerable, and cross-buntons require to be fixed, particularly in rectangular shafts, there is danger of the kibble catching these, and doing much damage to the sides of the shaft, and causing injury to the men at the pit-bottom. To obviate risks, guides are sometimes carried down as the sinking proceeds, and a ridor employed to run between the con- ductors and guide the kibble, and also to keep it from swinging. SINKING. 67 Fig. 75 shows the construction of a rider, made wholly of iron, to suit wire rope guides. Such a rider runs upon four bushes connected to the arms, the winding rope passing through an opening in the centre sufficiently large for the rope to pass through freely, but too small to permit the capping to do so. At a short distance from the pit-bottom conductors are fastened, or a projection is fixed to them, so that they may grip the rider when it reaches that point. The rope continues to descend through the central opening until the kibble reaches the pit-bottom, while the rider is securely held above. On the upward journey the rope runs through until the capping strikes the rider, which is then carried up to the surface, guiding the kibble during its ascent. Figs. 76, 77 show the details of the bush and gland which run on the rope at a a and /; h. Elevation. Plan. Figs. 75, 76, and 77. —Iron rider. When wood conductors are used a differently constructed rider is required. A form of conductor which is simple and efficient under these circumstances consists of four pieces of wood e e (figs. 78, 79), connected by two upright pieces // firmly bolted together. The space between these is filled by pieces of wood g //, and only an opening about 4 in. square is left in the centre for the winding rope to pass through. Near the bottom of the guides two cleats are fixed, h hy for the rider to rest on, while the kibble proceeds to the pit-bottom. On the capping of the rope one or two pairs of glands 1 are fixed, for the purpose of catehing the rider and carrying it to the surface during the ascent of the kibble. The advantages of using a rider during sinking are, that the winding of the kibble can be carried on at a much greater speed than if no rider be used while, as before stated, it is prevented from swinging about and so endangering the men working below. 68 PRACTICAL COAL-MINING. Elevation. The guides, if composed of wire ropes, should be frequently ex- amined and kept well lubricated, particularly during frosty weather. Great care ought to be taken to keep ice from forming on the guides, as such obstructions prevent the rider from running freely, and it may then stick in the shaft and perhaps fall away and do much injury. Fatal accidents have occurred through the rider sticking and then dropping away suddenly. ventnating Shafts during Sinkiiig. — While sinking is going on a suffi- cient supply of air must be provided at the bottom of the pit, to clear away the smoke due to blasting, and enable the men to work. This may be accomplished — (1) By dividing the shaft by means of a close brattice and connecting one side of the engine chimney or stack. (2) By carrying down a column of steam pipes ana allowing steam to escape through a jet or nozzle in the closed compartment of the shaft. (3) By ventilating the pit, by erecting either a temporary or the permanent fan and connecting it with the pit The first method is sometimes used, but, of course, would not be suitable Guide if fire-damp were expected to bt given off freely. Connecting the air drift to the flue of the chimney stack acts in the same way as a ventilating furnace Fios. 78 and 79.— Rider for wood underground by heating the air cur- conductors, rent, and thereby causing a circulation of air in the shaft. The steam jet is a simple and handy way of ventilating shafts during sinking, and can be very easily applied, particularly if steam pipes have to be carried down to pumps in the shaft. Often the heat given off by these pipes is quite sufficient to ventilate the shaft without the aid of a steam jet. Probably the best method is, however, to use a small temporary fan to force air down to the bottom of the pit. At Viewpark Colliery, Uddingston, while two shafts were being sunk, with" a distance of about 50 ft. separating them, a small fan was used, con- nected to both shafts by a wooden drift or box 3 ft. high and 2 ft. broad, and made of flooring deals closely jointed together. Each shaft was divided by a close brattice and a connection made to the fan drift or air box. Smaller boxes were carried down the shaft. Sometimes pipes of large diameter made of thin sheet-iron arc used Plan. instead of boxes. A force fan ia preferable to an exhatist fan for ventilating sinking ahafte, as the bottom of the pit, after blaatiiig, will be more quickly cleared, and the men can resume work sooner. Enlargmg Shafts. — Shafts sometimes become too small for the amount of work required to be done in them, and require to be enlarged. If winding has to be completely stopped and under- ground operations abandoned while such enlargement is taking place, the best method would be to entirely fill up the shaft with some light, loose material, and { start the enlargement from the surface, and carry on sinking in the usual way. If the regular work of the colliery has, on the other hand, to be carried on, and the shaft contains pipes, etc., which it is undesirable to interfere with, then enlarg- ing a shaft is not such an easy matter to accomplish. Kach case must of course be dealt with according to the circumstances. The enlarge- ment of a shaft of which tlie writer has personal know-^ ledge was carried out in the following manner. The colliery consists of two rectangular shafts, one bemg used as an up-caat and the other as a down-cast. The lining of the former showed signs of giving way, and the shaft had also departed from the vertical, while repairs of the wood lining had made it FiOB. 80 and 81. —Timbering of ihafU. smaller than it was origin- ally. It was determined to renew the whole of the lining, render the shaft vertical and enUrge it somewhat, while at the same time the whole of the winding was to be carried on at the down-cast. To have filled up the pit completely would have stopped venti- lation, and consequently stopped work by the colliers. The enlargement was therefore carried out in stages of 10 fms. or so, by putting in a scaffold, resting on strong beams, in the shaft, this scaffold being completely closed with the exception of an opening of about 4 ft. square, to allow of a wood box passing through tor 70 PRACTICAL COAL-MINING. the purposes of ventilation (see figs. 80, 81). This air-box, con- structed of planking 9 in. x 3 in., firmly fitted together, was carried down past the scafibld for a short distance, and also up to the surface, and connected to the fan. The shaft was now filled in with ashes to the surface. The enlarging of this portion of the shaft was then proceeded with and new lining put in. The other sections of the shaft were dealt with in a similar manner until the whole shaft had been renewed to a depth of nearly 200 yds. The work was carried out expeditiously, and the whole of the output was dealt with at the other shaft. This method may be easily under- stood from figs. 80, 81. Another method which the author has seen used for enlarging shafts is to use, instead of the wooden boxing described above, a wrought-iron or steel cylinder, 3 or 4 ft. diameter and 18 or 20 ft. long, an old flue of a Lancashire boiler serving well for the purpose. A strong scaffold is put in, leaving an opening for the tube to move through, and the pit is filled with ashes or other debris as already described. The tube is hung by a steel wire rope led from a steam winch on the surface, and as each section of enlargement is carried on, the tube is lowered so as to always keep the top of it a little distance above the fillcd-in debris. By this method a scaffold requires to be put in and the shaft enlarged in sections of 18 or 20 ft., or according to the length of the tube used. This system has the advantage that the iron tube is not so easily damaged as the wood boxing if J)lasting has to be resorted to. CHAPTER IV. EXPLOSIVES. Definition. — An explosive is a substance the decomposition of which results in the sudden expansion of its components into a volume of heated gases many times exceeding its original bulk. The strength of an explosive depends upon the volume of gases liberated, the rate at which decomposition proceeds, and the tempera- ture of ignition. The gases liberated by the ignition of gunpowder, for instance, amount to about 2000 times the original volume of the powder used. The force exerted by ordinary blasting powder has been ascertained to be about 22,000 foot-pounds per sq. in. The actual work performed by any explosive used in blasting operations is limited by incomplete combustion, compression, etc., by waste of energy in cracking and in heating material not displaced, and by the escape of gases through the shot-hole and through fissures in the rock. The efficiency of explosives, Le. the proportion borne by the work done to the theoretical energy liberated, has been estimated to range from 4 to 33 per cent. Olasaification of ExplosiveB. — Explosives may be classified in different ways, such as rending and shattering, or high and low, but the usual systems adopted are : (1) according to method of igniting ; (2) according to composition. Under the first head they may be subdivided as follows : — Explosives the decomposition of which is due to simple combustion, as in the case of ordinary gunpowder. Explosives in which detonation occurs simultaneously throughout their mass, as Ammonite, Amvis, Bellite, Roburite, etc. Explosives which partly detonate and partly bum, such as Carbonite, Kynite, Gelignite, etc. Classification according to Composition (Cundhill) : — Gunpowder, ordinarily so-called. Nitrate mixtures other than gunpowder. Chlorate mixtures. Nitro-compounds containing nitroglycerine, including the dynamite series. Nitro-compounds not contaming nitroglycerine, such as guncotton, etc. Miscellaneous explosives. 71 72 PRACTICAL COAL-MINING. Gunpowder is largely used. It is cheap, comparatively slow in action, and therefore suitable for coal and soft rocks, and less dangerous than some of the nitro-compounds. On the other hand, it is very dangerous in the presence of fire-damp and coal-dust, and its use is now prohibited in certain collieries by order of the Home Secretary.* Gunpowder, if exploded in large quantities, is also dangerous to life, owing to the large percentage of carbon monoxide it gives off, and no explosives which give rise to this gas ought to be used for extensive blasting in mines, because of the risk of injury to health, and also because even small traces of carbon monoxide have been proved to render mixtures of coal-dust and air highly explosive, a point fre- quently overlooked in experiments with explosives. On firing IJ lbs. of blasting powder, over 3 cub. ft. of combustible gas, consisting chiefly of carbon monoxide, would be produced, and this, when mixed with pure air, would give over 10 cub. ft. of an explosive, or, at least, a rapidly burning mixture. The approximate composition of ordinary gunpowder is : Nitrate of potassium (saltpetre), 75 per cent. ; carbon, 15 per cent. ; aulphur, 10 per cent. When gunpowder is exploded 56 per cent, of solid matter is formed and 44 per cent, of gas, or roughly, the solid matter is to the gaseous as 6 to 4. Ordinary blasting powder explodes at 600' F. By the explosion of ordinary powder the following gases are produced t : — Volumes per cent. Carbon dioxide, 32-16 Carbon monoxide. . 88-76 Nitrogen, 19-08 Sulphuretted hydrogen, . Marsh gas, Hydrogen, Volumes per cent. 7-10 273 6-24 100-00 From the foregoing it will be seen that gunpowder gives off a large percentage of carbon monoxide, which, as already stated, is very objectionable. The sulphur is also objectionable, and is by many makers reduced to a minimum. Gunpowder is very effective in breaking down coal, and is readily kept in good condition. The following are typical blasting agents of the gunpowder type : — Special Bulldog Bobbinite Powder. No. 1. Nitrate of potassium, . 84-86 62-65 Charcoal 12-18 17-19i Moisture, .... • • • 2i Carbonate of magnesium, . 24-8i • • ■ Sulphur • •• li-24 Sulphate of ammonium, .'l 18-17 Sulphate of copper, .1 • • * * See Coal Mines Explosives Orders, 1897-1904. t Ore and Stone Mining, Prof. Le Neve Foster, sixth edition, p. 223. Argus Powder. Earthquake Powder. 70-82 78-81 17-20 19-28 i-1 i (optional) EXPLOSIVES. 73 To be compressed to a pellet, density 1*42, and, in the case of bobbinite, to be coated with paraffin wax melting at 120*' F. Both explosives to be fired by electric fuse containing 5 grains of gun- powder, or with equivalent efficient explosive. Other varieties of gunpowder, introduced of recent years, are the following : — Constituents. Nitrate of potassium, Carbon, Distilled or pure sulphur, Oxalate of ammonium, ... Constituents. Elephant Brand. Oxalate Powder. Nitrate of potassium, . 74-76 63-73 Carbon, 14i-16J 12-16i Pure or distilled sulphur, 9-11 Oxalate of ammonium, . ... 18^164 Chlorate Mixtures. — Explosives containing chlorate of potash are regarded as too dangerous for mining purposes, being peculiarly sensitive to slight shocks, blows, etc. Nitrate M&tures other than Gunpowder. — In this class of explosives nitrate of sodium (Chili saltpetre) is substituted for potassium nitrate. Such mixtures are cheaper, but are absorbent, or deliquescent, i.^. they take up moisture from the atmosphere and are therefore unsuitable for mining purposes. Nitro-compounds containing Nitroglycerine. — In this class are included all those * high ' explosives which arc so useful in mining, and particularly in blasting operations in hard rock. Nitroglycerine is a light yellow, oily liquid, having a specific gravity of 1*6. It freezes at 40* F., and explodes with great violence at 360* F., or when subjected to a sudden shock. It is less sensitive to blows and detonation when frozen than when in the liquid state. Its use in the pure state is forbidden in Britain. Blasting GdcUine, — This is one of the most powerful explosives used in mining. Its manufacture is both difficult and dangerous, but when once made it is one of the safest of explosives. It contains 93 per cent, to 95 per cent, of nitroglycerine, and 5 per cent, to 7 per cent, of nitro-cotton. It is less rapid in detonation than dynamite, and is quite insoluble in water, in which it may be kept without deterioration. In its plastic state it is less sensitive to shocks or blows than dynamite, but when frozen it is more so. A rifle-bullet fired into a frozen mass of it causes an explosion, while no effect is produced by the same treat- ment in an unfrozen condition. Its relative sensibility to detonation compared with dynamite has been accurately ascertained, 0*8 grain of * cap mixture * being required to explode a given charge of No. 1 74 PRACTICAL COAL-MINING. dynamite, while the best blasting gelatine requires, for the same charge, 3 gmins. Relative efficiency of different explosives with same charge : — Blasting gelatine (93 per cent, nitroglycerine and 7 per cent, nitro cotton), Nitroglycerine, No. 1 dynamite, No. 2 dynamite, Gunpowder (extra strong), 1000-00 907-14 rt42-85 378-57 194-28 It will thus be seen that blasting gelatine is about three times more efficient than ordinary dynamite, and about fives times stronger than gunpowder. Dynamite. — This explosive is manufactured by impregnating diatomaccous Kieselguhr, a spongy earth obtained from Germany, with nitroglycerine. Its average composition is : Nitroglycerine, 75 per cent. ; kieselguhr, 25 per cent. When in a proper condition dynamite is plastic, may be safely handled, and is very convenient for use as an explosive. Irregularly shaped holes are easily charged with it, and it does not explode at ordinary temperature either by spark or flame, but requires detonation. When dynamite cartridges are at a temperature below 32' F. they will only detonate with difficulty. When their temperature falls below 40' F. they are not in a safe condition, owing to their increased sensitiveness to shock. When in a frozen condition they should only be thawed by the warming-pans provided by the makers, and not heated in tin cans over fires or carried about in trouser pockets, as is too often done by miners. Relative Efficiency of Gunpowder and Dynamite. For Equal Weights. For Equal Bulks. Gunpowder -- 1 '00 No. 1 dynamite =3*75 No. 2 dynamite = 2 -00 Gunpowder = 1 '00 No. 1 dynamite =6 -00 No. 2 dynamite = 3 '30 The use of dynamite results in economy of labour and tamping, loose sand being sufficient. It can be used in watery rock, and gives off but little smoke. Safety or Flameless Explosives. — In all fiery or dusty mines where it is absolutely necessary to prevent flame issuing from a shot on explosion, one or other of the numerous safety explosives must be used. The Home Secretary has it in his power to prevent the use of such explosives as he may deem unsafe for mines, and before any explosive can be considered safe for such mines it must be tested at a station provided by the Government for this purpose at Woolwich. The following is a complete list of the names of explosives permitted by the Act which came into force 1st January 1898, and was revised in EXPLOSIVES. 75 Coal Mines Orders of the 20th December 1902, of the 24th April 1903, of the 5th September 1903, and of the 10th December 1903 :— Alblonite. Ammonal. Ammonite Amvis. Aphoidte. Arkitc. Bellite No. 1. Bellite No. 3. Bobbinite. Britonite. Cambrite. Carbonite. Name of Explosive. Clydite. Coronite. Dahmenite A. Dragonite. Electronite. FaYersham Powder. Fracturite. Gelozite. HayliteNo. 1. Kynite. NeffTo Powder Noble Ardeer Powder. Nobel Carbonite. Normanite. Pit-ite. Robarite No. 8. . Sazonite. Stow-ite. Thunderite. Victorite. Virite. Westfalite No. 1. Wcstfalite No. 2. Other explosives are being tested from time to time and added to the list. It must be understood that the above list of permitted explosives does not form a guarantee by the Home Office that the explosives are safe under all conditions ; it only signifies that those named have passed the Woolwich test, and the mine-owner is left to choose the explosive that he thinks may be safest to use under the conditions prevailing at any given colliery. To assist mine- owners, however, the Home Secretary issued a notice in October 1899, intimating an additional test to which explosives already upon the 'Permitted List* might be subjected. The proposed test was more severe than the original one, and explosives which passed it w^ill be placed on a ' Special List.' The composition of these permitted explosives is as follows : — Albionite. Arkite. Britonite. Nitrate of potassium, 84-lOi 21-23 81-34 Nitroglycerine, 80i-83 61-54 25-27 Nitro-cotton, 6-7 3-4 • ■ • Wood-meal, . 2-3 6-8 89-48 Chalk i i • • • Oxalate of ammonium, . 14-16 ■ • • Carbonate of sodium, * • • ■ • • • ■ i The wood-meal to contain not less than 5 nor more than 15 per cent, of moisture. The cartridges to be of non- waterproofed parch- ment paper, and fired with an electric detonator No. 6. Carbonite. 26-27 1 30-36 39-42 i i • ■ • Wood-meal : moisture not less than 10 nor more than 20 per cent. Non-waterproof wrappers of parchment paper. Detonator No. 6. Cambrite. Nitroglycerine, 25-27 Nitrate of barium, . 8i-4i Nitrate of potassium, Wood-meal, .... 28-32 39-42 Sulphuretted benzol. Car Donates of sodium and calcium. i • Oxalate of ammonium, . • • • 76 PRACTICAL COAL-MINING. Ooronite. Nitroglycerine, 38 40 Nitro-cotton 1 IJ Nitrate of ammonium, 26 28 Nitrate of potassium, 3 5 Stearate of aluminium, 11 14 Rye flour, 8 11 Wood-meal, 2 4 Liquid hydrocarbon of the paraffin series, . ... 2 4 Moisture, 2} Wood -meal and rye-flour: not more than 15 and not leas than 5 per cent, of moisture ; hydrocarbon to have a flash-point not less than 200' F.; the stearate to be free from mineral acid. Waterproof wrapper. Detonator No 7. Clydite. Dragonite. Fracturite. Nitroglycerine, 26-27 34-37 614-684 Nitrate of barium, . 32-36 • • • « • • Wood-meal, . 384-41 i and charcoal 11-324 6-7 Sulphuretted benzol, Car Donate of sodium, 4 • • ■ • • • : :) * Carbonate of calcium. • • • • mm Oxalate of ammonium, . 8 • • • 1^-16 Nitro-cotton, ■ ■ • • • 2-3 3-4 Nitrate of ix>tassium. ■ ■ « • 43-4(5 21-26 Vaseline, • • • ■ • 6-6 » • • Non-waterpixx>f parchment wrappers. Detonator No. 6. Wood- meals (first two), 5 to 15 per cent, of moisture ; fracturite, 5 to 17 per cent. Nitroglycerine, Nitro-cotton, Potassium nitrate, . Wood-meal, . Ammonium oxalate, Red ochre. Nitrate of barium . Mineral jelly (acid free), Chalk, . Greloxite. Haylite No. 1. Kynite. 26-27 64-67 26-27 4-6 4-14 18-22 19-21 6-7 12-14 13-16 10-12 1 «•• • • • 19-21 • • ■ 6-8 39-42 30-86 Wood-meal, 5 to 15 per cent, of moisture (except kynite, 10 to 20 per cent.). Non- waterproof wrappers. Detonator No. 6. Nol»el Ardeer Powder. Nitroglycerine, . Kiese^hr, Sulphate of magnesium. Nitrate of potassium, . Carbonate of ammonium, Carbonate of calcium, Non- waterproof wrapper. Detonator No. 3. 31 34 11 14 47 61 4 6 • • • i • • • i EXPLOSIVES. Nobel Carbonite. Normanite Nitroglyoerine, • 26-27 32i-34i Nitrate of potassium, Nitrate of barium, . ■ • 28-82 42M6i • I 8i-4J • • • Wood-meal, . • 39-42 7-9 Sulphuretted benzol, • i • • » Carbonates of sodium and calcium. i • •• Charcoal, • * 1 t •• m 1-2 Ammonium oxalate. • ■ 1 • • • 10-12 Nitro-cotton, ■ • 1 ■ • • 1-2 77 Wood-meal, 10 to 20 per cent, of moisture. Non- waterproof wrappers. Detonator No. 6. Nitroglycerine, Nitrate of barium. Wood-meal Carbonates of sodium and calcium, Nitrate of potassium, Onalk, ..... Oxalate of ammonium, . Nitro-cotton, Pit-itc. 25-27 31-86 40-43 i Saxonite. 68-68 • • • 5-8i 21J-30J h 9-27 31-5i Stow-ite. 68-61 • • • 6-7 18-20 B • • 11-13 4i-6 Wood-meal, 5 to 15 per cent, moisture. Non- waterproof wrappers. Detonator No. 6. Nitroglycerine, Nitrate of barium, Wood-meal, Sulphuretted benzol, Caroonate of sodium, )^ Carbonate of calcium, Victorite. 25 27 32 36 38i 4U • • • n / Wood- meal, 5 to 15 per cent, of moisture. Non-waterproof wrappers. Detonator No. 6. Kitro^ompoimds not containing Nitroglycerine. — These have, as their base, nitrate of ammonium, mixed with other substances. The more important explosives of this class are : — Nitrate of ammonium, Wood-meal, Moisture, Di-nitro-benzol, . Chlorinated naphthalene, Metallic ammonium, . Di-nitro-naphthalene, . Amvis. Ammonal. Ammonite 88-91 4-6 93-97 ■ # 1 87-89 • • • 4 4-6 4-6 11-13 i4mvw.-- Chlorine not to exceed 1 per cent, of finished explosive. Special wrappers are required for all these explosives ; they are tired with No. 6 detonators. 78 PRACTICAL COAL-MINING. Aphosite. Nitrate of ammonium, . 58 62 Nitrate of potaesium, . 28 31 Charcoal, . . . . 34 44 Wood-meal, . . . . 34 44 Sulphur, 2 8 Moisture 14 Special wrapper and fuses required. Nitrate of ammonium, Di-nitro-benzol, . Moisture, . Naphthalene, Bicnromate of potassium, Bellite No. 1. Bellite No. 2. 82-85 92-95 15-18 6-8 I i Special wrappers, and No. 7 detonator. Dahmenite. 914-934 • • • 1 4-64 14-24 Nitrate of ammonium, Nitrate of barium. Wood-meal, Starch, Moisture, . Tri-nitro-toluol, . Chloride of ammonium, Chloride of sodium, . Electronite. 71-76 18-20 7-10 i Faversham Faversham Powder No. 1. Powder No. 2. 84-86 4 10-12 1-2 2-8 87-98 1 9-11 Electnmite. — Wood-meal to be charred. Lead waterproofed case ; detonator No. 7. The Faversham powders are not specially indicated. Nitrate of ammonium, Tri-nitro-toluol, Graphite, Colouring matter. Moisture, Special cases. Detonator No. 6. Negro- Powder. 86 90*0 9 11 0 1 3-0 0-1 1-0 Nitrate of ammonium, Di-nitro-benzol, Tri-nitro-benzol, Chloro-naphthalene, Flour, Moisture, Roburite No. 3. Thunderite. 86-89 91 93 9-13 • ■ • • * • 3-5 2 .. • • • 3-5 i 1 Special wrappers. Detonators No. 6 and No. 8 respectively. EXPLOSIVES. 79 Virite. Oxalate of ammonium, 9 12 Nitrate of ammoniam, 35 40 Nitrate of potassium, 33 38 Sulphur, 4 5 Charcoal, lOJ 124 Moisture, 1 2 Special wrapper. Electric fuse containing 5 grains of gunpowder or equivalent explosive. Westfalite. No. 1. No. 2. Nitrate of ammonium, 94-96 90-92 Nitrate of potassium, 3-5 Resin 4-6 4-6 Moisture, 4 4 Special wrappers and No. 7 detonator. Detonators. — These are generally made of copper caps containing a small quantity of fulminate of mercury, or a mixture of fulminate with chlorate of potash, the proportion of the latter varying from 5 to 40 per cent. The Home Office issued an order in 1897 regarding the standard charge for detonators, which is to consist of a mixture of fulminate of mercury 80 per cent., and chlorate of potash 20 per Cent., or some other explosive mixture of the fulminate class of not less strength than the above. Different explosives require detonators of different strength to explode them, and the manufacturers of explosives generally recommend a certain class or strength of detonator for use in blasting the different explosives which they produce. These strengths are usually denoted by numbers, and the following are those commonly in use : — No. I. No. 2. No. 3. No. 4. No. 6. No. 6. No. 6}. No. 7. No. 8. Charge per 1000 jg^^ ^^^ 5^q ^^q g^^ j^q^ ^250 1600 2000 m grammes . | IndividualchargeK.g g.g g.g i^ ^g-S 15-4 19-2 23-1 30*9 m grains . . j For rending explosives — e.g., some of the blasting powders, Nobel Ardeer powder, etc. — a detonator of the strength of No. 3 is commonly employed ; for explosives of the nitroglycerine class No. 6 or No. 6 J is the most suitable. Miners and shot-firers should therefore be pro- vided with the class of detonator most suitable for the explosive they are using. As the whole success and safety of shot-firing almost entirely depends on the detonators, it is of the utmost importance that not only the proper strength of detonator be used, but also that the detonators be of a good quality. A common source of annoyance and danger in using inferior or under-strength detonators is miss-fires, which should be avoided at all hazards. Miss-fires, however, may 80 PRAcrriCAL coal-mining. occur with the best quality of detonators if they are not carefully handled and stored. Detonators should be kept in a dry place, and under no circumstances should they be placed in sawdust, as is sometimes done, for they absorb the moisture from it and soon become useless. They should also be bought in such quantities as will suffice for short periods, as they soon deteriorate if kept in store. In taking them into the mine, detonators ought to be carried in a securely locked case or bag separate from the other explosives. Fixing tJie Detonator. — To fire a shot, a piece of fuse, of sufficient length, is taken, cut clean, and inserted into the open end of the detonator, which is then inserted into the cartridge of explosive, taking care to have the detonator so placed that the explosive covers it. After placing the detonator in position, it should be securely tied to the cartridge with a piece of string. When placing the charge in the shot-hole the detonator end of the cartridge should be towards the mouth of the hole, one detonator only being used for each charge. Precautions against Fire-damp Explosions. — In order to avoid the danger of fire-damp explosions, arising from shot-firing, in fiery mines, strict observance should be paid to the following rules with regard to the detonator : — (1) Explosives should always be exploded by a sufficiently powerful detonator. Newly-introduced explosives should be tested first to ascertain the strength of the detonator required. (2) The fulminating portion of the detonator must be properly enclosed, for only such caps can be depended on as do not sutler from leakage. (3) Detonators should be tested to see if they are in ^ood condition. (4) Wherever possible, detonators should be specially re-dried before being used. (5) If explosion is to take place in wet or damp ground, the point of junction with the friction fuse should be well protected by some waterproof covering. * Friction-detonators, i.e. detonators which are fixed to the fuse when manufactured, are safer duriug transport, less liable to be jarred in tamping, and safer to handle. Finng the Charge. — Except where blasting is done by electricity, the charge is fired either by germans, squibs, or safety fuses, the latter being most largely employed in coal-mining. Germans or squibs consist of small cylinders of cardboard or stiff paper filled with gunpowder, and are inserted into the shot-hole. To the outer end a piece of cotton wick, saturated with oil, is attached. When the charge is ready for firing, the wick is lighted. Safely Fuses. — Many safety fuses have been devised. They mostly consist of a fine column or central core of gunpowder, surrounded by flax, cotton, or similar materials. Taped fuses are protected by an external varnished coating, and are adapted for use in wet ground. In using such a fuse, the charge to be fired must be enclosed in a cartridge, into one end of which the fuse is introduced. The gutta> * Trans. F^d. Inst. Mi't. Engs.^ vol. x. pp. 550-557. percha fuse is surrounded by a coating of that nuiterial, and has also an outside coating of waterproof vaniished cloth, so as to preserve the guttapercha, as the latter becomes very brittle when exposed to air. Fuses should be kept or stored in a dry place, so that the core of powder may not be affected by damp, ana care should be taken that they do not come in contact with greasy or oily matter, as this rapidly penetrates the outer covering to the gunpowder and prevents the proper burning of the fuse. Ordinary fuse bums at the rate of about 3 ft. per minute. The disadvantages of using ordinary safety fuses are : (a) Uncer- tainty of burning speed of the fuse ; (fr) danger of missfires through defective fuse ; (r) dangers of shots hanging fire ; (d) ignition of explosive gases from * spit ' of safety fuses ; {e) ignition of explosive gases from burning fuses ; (/) dense smoke given off from the burning fuses. Firing SJiots hij Electricity, — In many collieries, especially those in which safety lamps are used, or which are dry and dusty, it has now become the custom to fire the shots by electricity. There can be no doubt but that this system of firing shots, when properly carried out, is very much safer than blasting with the ordinary fuse and detonator, as it allows the workmen to retire to a place of safety before the charge is exploded, and there is much less danger from ' hang-fire ' or ' miss-fire ' shots, or from the premature explosion of the charge. Klecti'ic Fuses, — In exploding charges of explosives by electricity, fuses, or detonators with wire attachment, are used. These fuses are generally of two kinds, viz., high- and low-tension fuses. High- tension fuses have their terminal wires bridged by a chemical paste or priming powder of relatively high electrical resistance. When a current is sent along the caBles *' the electrical energy at the fuse (wire) terminals is (owing to the insufiicient conductivity of the bridging composition) converted into heat energy ; the heat cannot dissipate with sufficient rapidity, therefore the temperature rises to the point of ignition of the bridge or priming. The latter bursts into flame and in turn fires the explosive compound at the end of the copper cap " ; or, simply, the explosion is caused by the electric current heating the priming compound to ignition point. In the low-tension fuse the terminal wires are connected or * bridged ' by a short bridge of fine iridio-platinum wire (the wire is an alloy of 80 per cent, platinum and 20 per cent, iridium). The current in passing through this bridge raises its temperature sufficiently high (due to the same cause as in the high-tension fuse) to ignite the priming ; the priming in turn, as above, fires the fulminate of mercury compound. In the Dortmund district of Germany, fuses called 'Spaltgliihziindor,' occupying an intermediate position between high- and low-tension fuses, are used for firing single shots. They are essentially low- tension igniters, but the platinum bridge is replaced by a finelv " ^ 82 PRACTICAL COAL-MINING. divided conducting substance, such as graphite or coal-dust, mixed with the igniting substance, and the resistance opposed to the current is far greater than that of a small platinum wire, being generally about 5000 ohms. The quantity of current required to ignite the few particles of dust between the wire terminals is very slight, not exceeding at most yq^xt^^^ ^^ ^^ ampere. Such igniters are said to combine the advantages of both the high- and low-tension fuses without their disadvantages. Exj)loder8. — For igniting or exploding the fuse, small electric machines or exploders are used, that most largely employed being known as a magneto-exploder. It consists essentially of an armature, revolving between the poles of a set of permanent electromagnets of hardened steel. The armature, which is wound to a high resist- ance, is made to revolve rapidly by means of a rotary crank connected to geared wheels in contact with the armature spindle. By this means an electric current of high potential is generated sufficient to explode the fuse. A flu id ic or dry battery and secondary battery exploders are also used for the electric firing of shots in mines. Firing Cables or Gonductimj Wires, — In order to allow a safe distance between the blasting charge and the shot-fircr, a suitable length of cable, for conveying the current, must be employed to comiect the exploder to the fuses. The length required will depend upon the nature of the blasting, i.e, whether it is in rock or coal, and the place where the shots liave to be fired, but the minimum length should not be less than about 50 ft. for coal, and a longer length for stone-work in narrow drifts. The most suitable length, however, to be used in every colliery cannot be arbitrarily stilted, but must be fixed from what is found to be best by practical experience. Simidtaneom Firing. —When blasting with electricity in shaft sinking or stone drifts, the shots are ignited simultaneously in order to obtain the maximum rending effect, although it is questionable if this effect is always got from such a method of bhisting. Some persons, indeed, hold that independent firing gives much better results, for the reason that if all the shots are ignited at once it cannot be expected that one shot will help the other; but if the centre charges, say in a stone drift or at the bottom of a sinking pit, are fired first, so as to loosen the middle portion, the side charges should then operate under the mast favourable conditions. To enable shots to be fired independently with electric blasting, a system has been brought into use by the adoption of a combination of electric ignition and tape-fuse. By this system a reUirding action is got by inserting a piece of tape-fuse between the electric igniter and the detonator. For simultaneous firing two systems of connect- ing the fuses to the exploder are usually employed, known as the series and parallel systems. In the series system the line and fuse wires are coupled consecutively, one wire of the fuse l)eing connected direct to the cable, the other wire connecting the first shot to the EXPLOSTVKS. 83 second, the second to the third, and so on until all the charges are joined up, after which the remaining wire is coupled up to the second cable. Low-tension fuses are generally fired by this system. With the parallel system the two firing cables are connected to the last charge, forming a parallel line, and then the wires of the other fuses are coupled up to them alternately. Where electricity is not employed ior blasting, simultaneous firing of a number of shots can be carried out by using the Bickford patent volley-firer in conjunction with the same maker's instantaneous fuse. This appliance consists of a little instrument devised so as to contain an ordinary safety fuse at one end and at the other a set of instan- taneous fuses, the set varying according to the number of charges to be blasted. Between the end of the safety fuse and the ends of the instantaneous fuses is inserted an explosive disc, the action of which is such that, on the communication of fire from the safety fuse, the whole of the instantaneous fuses are immediately ignited, the latter burning at the rate of about 100 ft. per second, giving practically the same result as with electric firing. Any number of shots up to sixteen can be fired simultaneously by this apparatus. lyniting Shots in Fiery Mines, — In fiery mines or mines where safety lamps are exclusively used, and where blasting has to be done, the ignition of the shots may be carried out by (a) safety lamp; (6) special contrivances like Bickford's patent fuse lighter; (c) by electric firing. Electric blasting has already been fully dealt with. Bloum-out Shots. — These may be a source of great danger in mines which are dry and dusty and where fire-damp is given otf. They ought to be carefully guarded against in blasting. Blown- out shots hre brought about chiefly by (a) insufficiently and badly tamped holes ; (b) an insufficient charge of explosive for the work to be done ; (c) the shot-holes being drilled beyond the line of holing or kirving. The charge should be w^ell, but not excessively, tamped with good surface clay or fireclay, free from stones or hard nodules, the tamping being firmly rammed back with a wooden stemmer. The hole should not be drilled beyond a point 6 to 8 in. from the back of the holing, and in stone work especially, where the holing has often to be blasted out, the holes should be drilled at a suitable angle and length according to the kind of explosive used. Position of Shot-holes, — The most suitable position for the charge depends upon various circumstances, a proper knowledge of which can only be obtained by actual practical experience. All 'joints,' * backs,' * lypes,' * partings,' etc., must be carefully avoided, and the position of the hole for the charge so placed that the resistance in every direction may be as nearly equal as possible from the expected plane of fracture. As an explosion takes effect along the line of least resistance, if there are any joints or cracks near the hole, they will deteimine the direction of fracture, and the charge will have comparatively 84 PRACTICAL COAL-MINING. little effect in any other direction. In the case of a sump-hole, for instance, in a sinking pit, the line of least resistance will be the shot-hole itself, and in such a case a heavier charge of gunpowder than ordinary must be used, and it will have to be well stemmed, or a strong explosive occupying little bulk must be employed, such as dynamite. Prevention of Flame Gommnnication. — The Water-cartridge, — In the presence of fire-damp, what is known as the * water-cartridge ' is used, in conjunction with dynamite or other explosives. The water-cartridge consists of a cylindrical case of specially prepared waterproof paper 18 in. long and 2 in. diameter. In the centre of this case is placed the explosive, kept in position by thin metallic webs, the end of the cartridge having the detonator for electric firing fixed to it by wire. The space between the charge and the paper cylinder is filled witli water, and the outer end firmly tied round the projecting wires. The water-cartridge is most largely used for dynamite blasting, but it cannot be said to give very satisfactory results, and has only been used to a very limited extent. The difficulty hitherto experienced with the water-cartridge is that the water is so liable to escape and the blast takes place in an empty cartridge. Instead of using water alone, a mixture of soap and water has been tried and found more reliable and effective. The water and a certain proportion of soap are first boiled together, and the resulting viscous liquid is then filled into an india-rubber bag or cartridge, and used in much the same way as the water-cartridge. Any other cheap gela- tinous compound may be used for the same purpose. Wet Sand, — Sometimes common sand, moistened with water, is used ; the cartridge containing the charge being placed in the centre of a paper covering made large enough to admit of \ in. of sand being placed all round it. The paper cartridge should be made thoroughly water-tight by being soaked in oil or grease and then allowed to dry. Wet Moss, — Stemming the charge with wet moss is another means employed to prevent fiame being communicated to the surrounding atmosphere, and is said to be effective when used with gelatine and dynamite. The same result may l>e obtained by using a stemming of moist clay, and probably this is as effective as anything which may be used. Cost of Blasting, — This will vary greatly according to the kind of explosive used, the system of firing adopted, and the hardness of the coal or strata the shots are fired in. The cost for blasting will varj' from about 0*35d. told, per ton, or an average of about 0*7d. per ton in coal. Regarding the cost of firing shots in gaseous mines — exclusive of explosive and labour — by different systems, i.e, firing by low^ and high-tension electric safety fuses, and by the Bickford patent lighters and.safety fuses * — Mr Frank W. T. Brain, in his evidence before th^ * Soe Report of CommitUet p. 483t £5 0 0 0 5 0 0 2 6 £5 7 6 BXPLOsivEa 85 Departmental Committee on the use of electricity, gave some figures which are instructive, and are here reproduced : — I. Cost o^ firing 1000 Sliots wJien using High-Tension Electric Detonators, 1000 4 ft. wirea, electric high -tension, No. 6 detonators, complete, ...... 50 yds. firing cable, costing lOs., ased, say, for 2000 shots, ....... Magneto exploder, costing 35s., plus repairs 10a., used, say, for 30 shots per day, two years, ToUl, Cost per shot = 1 *29d. II. Cost of firing 1000 Shots when using Low-Tension Electric Detonators. 1000 4 ft. wires, electric low tension, No. 6 detonators, complete, ...... 50 yds. filing cable, costing 10s., used, say, for 2000 shots, ....... Magneto exploder, costing 85s., plus repairs 10s., used, say, for 30 shots per day, two years. Total, Cost per shot = 1 *48d. III. Cost of firing 1000 Shots when using Bick/ord's Patent Safety Fuse and Igniters, 4000 ft. Bickford's fuse, ..... 1000 Bickford's igniters, ..... 1000 No. 6 detonators, ..... Total, Cost per 8hot=2'17d. From these figures it will be seen that the high-tension system is 0*1 9d. per shot, or approximately 13 per cent, cheaper than the low- tension system, and firing by the Bickford fuse and igniters shows a •difference of 0*88d. and 0'69d. per shot respectively for high and low- tension fuses, or a difference in favour of electricity of 68 per cent, •and 46 per cent, respectively, for high and low-tension fuses. It must be distinctly noticed that these figures are a mere comparison «of the cost of material alone. On the whole, firing by electricity is cheaper. Regarding the total •cost of blasting, i,e. including explosives, fuses and labour, it will vary .greatly according to the kind of explosive used, the system of firing £5 16 0 0 5 0 0 2 6 £6 3 6 £4 8 4 3 2 6 1 15 0 £9 0 10 86 PRACTICAL COAL-MINING. adopted, and whether the colliery is a non-fiery one or a fiery, dry and dusty one. Naturally in the latter class of mine the cost will be somewhat higher than for non-fiery mines where open lights are used. The average cost for blasting with gunpowder is about 0*6d. per ton, and for safety explosives 0'9d. per ton of coal got, or a difference of 0*3d. per ton in favour of gunpowder, so that the cost for blasting is increased about fifty per cent, when safety explosives are used. With gunpowder the percentage of round coal got, in a number of experi- ments, averaged 62*2 per cent, and for safety explosives 62*0 per cent., so that so far as this is concerned there is not much difference between gunpowder and some of the safety explosives. In blasting rock there is, however, an estimated gain of 25 per cent, in using the latter.* It may be taken for granted that many of the safety or permitted explosives are 50 to 100 per cent, dearer than blasting powder, but of course, on the other hand, a much smaller charge of such explosive will be required to do the work than if gunpowder was used. • Paper by Henry Hall, H.LM. CHAPTEB V. MECHANICAL WEDGES, ROCK DRILLS, AND COAL- CUTTING MACHINES. Mechanical Wedges in Goal-mining. — In underground excavations the coal seam or rock can very rarely be removed by the aid of picks alone, unless in very soft strata. In ordinary seams wedges are used to assist in bringing down the coal after it has been * holed * — the commonest form employed being known as the * feather-shaped ' wedge. This wedge is also an adjunct to blasting in many mines ; the coal being first loosened by explosives and afterwards wedged down. Elliott Multiple Wedge. — In mines where blasting is prohibited, some mechanical method must be adopted for bringing down the coal or rock without the aid of explosives. The Elliott wedge is designed for such a purpose, and may be said to be an adaptation of the old plug and feather. The construction and use of the wedge will be understood from figs. 82, 83. To use the wedge a hole must first be bored out deep enough to hold the wedges. Into this hole are then inserted two portions of the wedge a a, tapered in front and increasing in thickness towards the further end. These pieces are constructed with the front portion turned back so as to grip the hole and prevent them from being driven out of position. Two other long-tapered wedges h h are now driven into the hole, and if these fail to bring down the coal, a third wedge, d, may be driven in between them and thus exert further pressure. The advantages claimed for this wedge are that only a small hole requires to be bored, that the expansive force developed is great, the weight of wedges, etc., is small, and the first cost low. The wedges are made in two sizes : for holes \\ in. diameter, 2 ft. 6 in. long; and for holes 2 in. diameter, 3 ft. long. Burnett's Boiler Wedge. — In using the multiple wedge a great amount of power is necessarily lost in overcoming the friction of the parts sliding over each other, and the Burnett roller wedge has been designed to obviate this loss. In this appliance, the wedges, instead of being in sliding contact with the feathers or cheeks, are in rolling contact only ; and as the rollers are arranged on each side of the 87 88 PKACTICAL COAL-MINIHG. wedge, it will be underetood that the latter travels twice the duttanca jvered by the rollers on the a velocity ratio equal to only half that of the advanciug wedge. The power ia thus doubled and the friction greatly reduced. The construction of the wedge will be seen from figs. 84-89. A ia the wedge-bar formed in continuation of the plane A' and of the screw A*. The phiin part, A', ia en- closed between two bars or feathers B B', which are placed iu the bore-hole as shown. These ha.Ts are formed with a taper corresponding to that of the wedge, and the bottom feather Bx, which has to bear the greater strain, is made stronger than the top feather B. The rollers CC are placed near the end of these feathers B B'. A nut £, placed on the screw, affords facility for pulling the inner wedge-bar A out towards the face of the coal, whereby the rollers C C, while ascending on the inclines of the inner taper bar A and the inclines of the outer taper bars B and B', force the two latter apart to the re- quired extent. The nut E is formed with a flange, which is held in position by means of a bearing plate Ei, living lugs as shown. On the nut E, at its outer end, is formed a square, E*, on which is tiied a ratchet lever. Ajiplication of Weili/e. — The ^2^ ^^ necessary holing having been ^^P ^f completed and the coal drilled, F[.i8. 82 sDd 83.-ElUott multiple ^'^^ "«lge "A inserted. The wedge. ratchet lever K is then applied to £*, which, in working, rotates the nut £, which, bearing against the shoulder D, begins to draw MECHANICAL WBDGBS, ROCK DRILLS, KTC. 89 out the wedge A. The operator cotitinuea this direct action of the handle until more power is required than can be thus directly obtained. The ha:idle K is then shifted on to the square H' of the lever H, and by imparting successive oscillations to the same, the roller H^ acting against the cam slot G' of the fork G, will cause the pawl (fig. 87) F to pass a tooth at each oscillation of the lever, and thus power in direct proportion to the ratio of the leverage between H and G will be developed. Fios. 81, 85, 86, 87, 88, and 89.— Bumetfa roller wedge. Hydraulic Wedges. — Water at high pressure has been used as a means of blasting, but, eicept with the Tonge hydraulic cartridge, the success of hydraulic blasting has been questionable. Tonge Hydraidir, Cartridge. — This cartridge has been introduced into a number of collieriee in the Lancashire coal-field, and has given such satisfactory results that in oue or two mines it has entirely superseded blasting by explosives. The cartridge consists of a cylinder of steel 20 in. long by 3 in. in diameter, and having eight small duplex rams fixed radially along it By a suitable arrangement of passages, a communication is made between each of these rams whereby simultaneous action can be obtained. By an ingenious contrivance a greater traverse is obtained by these rams than the diameter of the cylinder. This traverse is essential for the complete forcing down of the coal. Thin liners are used to prevent the rams cutting into the coal. The cartridge is operated by a hydraulic pump, to which it is 4»>nnected by a pipe. The pump is of special design, is mounted ou 90 PRACTICAL COAL-MINING. an adjustable stand, and fitted with water tank. The water required Tor the whole of the operation is about one and a half pints, but moat of this returns to the tank at ita completion, and can bo used again. At the oommcncetuent of the operation the small handle is used, and when pressure has increased, an extension handle is slipped over it, and greater power is thus exerted. A pressure of 3 tons per square inch can be reached, and this represents a total pressure on the coal of over sixty tons. This is found adequate in ordinary seams, and the standard sizes are made for this duty. Special cartridges arc made for extraordinary conditions. Fta. 90. — Tonge hydraulic cartridge, showing rams extended after use. After the coal has been undercut, either by hand or coal-cutter, a hole 3J in, diameter is drilled' about 3 or 4 ft. deep into the (slightly leas than depth of holing). This is done by mean ordinary machine and spiral drills. The hole is put in parallel the roof, and as near as possible along the parting to which the ordinarily comes off, or just below it. It is then cleared out. The cartridge, with one or more liners, and having pipe and pump attached, is pushed to the back of the hole, and the pump is left in position for the attachment thereto of the stand, which is adjusted to the required height. The water tank is filled, and himg on tho pipe, the rubber suction pipe coupled, and the taps turned. The coal spn^ are all left in tight. The pressure being fully on, the coal is heard to be rumbling and cracking. This is allowed to continue until the back portion of the coal is broken off, after which the sprags are slightly slackened. By a contiauaoce of the pumping, the pressure is brought to bear at the front of the faces, and continues to spread until the operation is completed, when the MECHANICAL WEDGES, ROCK DRILLS, ETC. 91 eprags are then withdrawn. The whale operation occupies about ten minutes. This system saturatly secures absolute immunity from eiploeioD, mise-fireB, poisonous fumes, etc., while it is claimed that the coal is not so shattered. It has been in use three years at the AthertOD Collieries, 19,000 shots having been made in one seam in a year, producing 40,000 tons from a 3 ft. seam. Bock Didlls. — Rock drills may be divided into two classes, viz. — (1) hand drills, (2) machine drills. In the first class the work is performed by manual power alone, while in the second class other methods are employed, such as hydraulic pressure or com- pressed air. Hand Drills.— The commonest type of this class is that known as the ordinary ' ratchet ' boring machine, which is now so extensively Fia.fil.— Hand drill. Via. 92. — ' ConqDeror' machine. used in all kinds of mining. It consists of a scrcw-spiudle a (fig. 91), terminating in a hollow square, into which the drill e can be inserted, and working through a screw-nut collar h, which is fixed to, or composes part of, a hollow sheath «, for the screw-spindle to work in. When a hole requires to be bored, a prop is set firmly up, and the drill fixed against it with the boring-bit e inserted into a small hole or cut made with the pick in coal or rock. The handle c, which works on the ratchet d, is then turned and bores out the hole by a grinding action. When the full length of the drill is out, it is again worked back into the hollow sheath and a longer drill substituted, the same process being repeated until the hole is bored to the required depth. These machines are very handy, and will penetrate very hard stone. In the ' ratchet ' machine a prop has to be used to 92 PRACTICAL COAL-MINING. support the machine, and where hard rock has to be bored it is often difficult to keep the drill in position. To overcome this difficulty and save loss of time many machines are now provided with adjust- able stands. In the 'Conqueror' boring machine such a stand is provided, and the screwed nut and hollow sheath is done aw^ay with, the screw-spindle actuating the drill working through a long screw thimble a (fig. 92), which can be fitted on any part of the stand to suit the height of working and position of hole. An iron sole-piece is used on which the machine may stand, the height of which can be varied by the adjusting screw, which at the same time tightens it between the roof and floor. There is also an adjusting sliding piece b for regulating the position of the boring bit. The drill can be worked either with one or two handles, according to the hardness of the material and the power required. Machine-power Drills. — This class of machine has proved of great service in certain kinds of work. These drills are not so largely employed in coal-mining as in tunnelling, metal-mining, and quarry- ing, but there are often cases, such as the driving of mines in hard rock, sinking shafts through igneous rocks, etc., where they can be used with great advantage as auxiliaries in coal-mining. Possibly the fact that they require to be supplied with motive power such as steam or compressed air, the use of which involves considerable first cost in plant, and that skilled men are required to work them properly, will be against their extensive use in small coal-mines. There are, however, many collieries where compressed air is used for numerous purposes, amongst others for driving coal-cutting machines, and, in such circumstances, machine drills might be advantageously used. In order to obtain the greatest benefit from the use of rock drills in sinking or tunnelling, it is necessary that a given length be driven by each series of holes, and that all the holes of each series should be fired simultaneously, either by electricity or by a quick-burning fuse. The special point in favour of the use of rock drills in hard stone is that the same work is effected in about half the time that it could be done by ordinary methods. The following average weekly results have been obtained in sinking shafts by the aid of rock drills,, the rate of wages being that prevailing in 1894.* Cost per Yard. Depth «7 1? 1 ' Total cost. Shaft 18 ft. diameter. sunk ^*«^ ii^xplosives. ^^ ^^^ Feet. £ s. d. £ s. d. £ s. <£. Very hard limestone with partings, . . . 30 10 4 9 1 18 0 12 2 9* Coal meatsures, shales, and sandstones, . . 39 7 12 6 0 19 0 8 11 & • Trans. Inst, Min. Eags., vol. viii. pp. 18-19. MECHANICAL WEDGES, ROCK DRILLS, ETC. 93 The depth sunk by each series of holes was : — Hard limestone, . 4} feet in 18 hours. Hard sandstone, . 6J ,, 18 „ Shale and sandstone, 6J ,, 16 ,, The weight of stone lifted with each round of shots averaged, for hard stone 130 tons, and for moderately hard stone 150 tons. These figures are significant, as the cost of sinking would have been at least 25 to 30 per cent, higher if the ordinary methods had been adopted, while the rate of progress is very much greater, which is an important factor in all sinkings. Of course there is the additional cost of plant and oonsumpcion of fuel to be taken into account. In the case cited, where four drills were used, an air-compressor having a cylinder 1 6 in. diameter by 24 in. stroke, with a 20 nominal horse- power boiler attached, was required. Each drill when working con- sumed about 30 lbs. of coal per hour, or taking the working time of the drills at four hours per day, the consumption of four drills would be about 480 lbs. There are so many different kinds of machine drills in use that it would take up too much space to attempt to describe them all, and all that will here be attempted is to instance a few of the best known. Before doing so, it may be pointed out that the requirements of a good rock drill, as concisely stated by Andr^ * in his work on coal- mining, are as follows : — It should be simple in construction and strong in every part. It should consist of few parts, especially of few moving parts. It should be as light in weight as is consistent with the first condition. It should occupy hut little space. The striking part should be relatively heavy, and should strike the rock direct No other part than the piston should be exposed to violent shocks. The piston should be capable of workine with a variable length of stroke. Sudden removal of the resistance should not cause it any injury. The rotary motion of the drill should take place automatically. The feed, if automatic, should be regnlatea by the advance of the ]nston as the cutting advances. The machine should be capable of working with a moderate degree of pressure. It should be capable of being readily taken to pieces. Darlington Drill. — This is one of the simplest and most effective machines in use. It consists essentially of two parts : the cylinder A (fig. 93), with its cover, and the piston with its rod, to which is attached the boring tool c. To give the latter a rotary motion, there is a spiral or rifled bar H, having three grooves, and being fitted at its head with a ratchet-wheel e, recessed into the cover of the cylinder. Two detents // (fig. 95) are also recessed into the cover, and are • 4 PractHal Treatiie on Coal-Mining, by G. Q. Andr^, p. 148, 94 PRACTICAL COAL-MINING. made to fall into the teeth of the ratchet-wheel by spiral springs. This arrangement of the wheel aiid the detents allows the spiral bar H to turn freely in one direction, while it prevents it from turning in the contrary direction. The spiral bar drops into a long recess in the piston, which is fitted with a steel nut, made to accurately fit the grooves of the spiral. Hence the piston during its instroke is forced to turn upon the bar, but during its outatroke it tunis the bar, the latter lieing free to move in the direction in which the straight outstrokc of the piston tends to rotate it. Thus the piston, with the boring tool, asaumea a new position after each stroke. The total length of the Darlington drill is 3 ft., and the weight 100 lbs. Fioa. 93, 9<, and S5.— Darlington drill. Adelaide DrilL— The Adelaide drill somewhat resembles the Darlington maehtne just described, but in it the air is used ex- pansively, and it has only one moving part. The piaton c (figs. 96, 97) works in a cylinder, having porta and passages no arrang^ that the air or steam is admitted and cut off automatically by the piston il«elf. Air enters through an annular port A, by which means the pressure is equalised on all sides of the pistou-rod and unequal wear is avoided.* The cihaiist takes place through the port B. The piston itself is made to perform the action of a valve in the following manner : as soon as it reaches the port R, free communic^ition is opened with the • Journal BrU. Soc. Min. SludenU, col. liii. j.p. 70, 71. MECHANICAL WRIWES, BOCK DRILLS, ETC. 95 atmoepbere and eihaust takes place, not only here, but also through the ports Bj, which have by this time paesed outside the cyhnder cover. The inlet aperture A being always in free connection with the air receiver, tlie pressure now acta on the small area at the front of the piaton, and drives it backward, until this part is also FlQ. ea.— The Adelaide drill. brought into connection with the exhaust ; at the same moment, the ports B, come opposite the inlet A, compressed air entera through the hollow rod C, passes into the back end of the piston, and drives the drill rapidly forward against the rock. Admission takes place during half the stroke, the air i working expansively during the ' second half. To rotate the drill there is a spiral or rifled bar D, having three grooves. It is fitted at its head with a ratchet-wheel E, — — which is recessed in the cover of the cylinder. Two detents or cams, also fixed into the cylinder cover, are forced by small springs to engage with the teeth on the wheel E. The feed is obtained through the rotation of the screw H in the nut G. As the admission both below and | above the piston takes place some k,o. s7.-8ection of Adelaide drill, time before it arrives at the end of the stroke, a cushion is formed, and the piston is thus prevented from striking the covers. Ingenoll SrilL — Fig. 98 shows the construction of the Ingersoll eclipse drill which is so largely used in American mines. Eitlier steam or compressed air may be used as the motive power. The machine consists of the cylinder A, with the piston M, and the piston- rod B. Stoam or air is admitted by a single spool valve C, and enters the valve chest at ", and when the piston has reached the end of its back stroke it passes round the valve to the passage N', and then enters the port P', and ultimately reaches the back end of the 96 PBACrrCAL C0AL-MIK1N; •§00 5» 11 4» 1- 5»5 5^ A, . . . 29 12(1 17 bS 78 2 2 B, . . . 1 • •• 2 2 1 3 15 2 1 2 C, . . . • •• • • • • • • « 2 1 2 3 7 D, . . . ■ . 3 1 8 • • • • ■ a • •■ U 2 K. . . . • •• • •• 1 • « • • • 2 • •• 4 1 2 F, . . . 3 .S3 • • ■ • • • • •• ■ •• • •• • ■ «•• • ■• • •• ■ •• ToUl, . 52 23 30 129 23 70 93 22 • • • 6 2 A, Disc nuchines ; B. Pick (Iiifferenll or Hullivan); C, Revcilring bar; D, Rotary header • B, Toothed endless chaiu; F, not 8iiite«i. ' COAL-CUTTISG BY MACHINBBT, 99 Classification of Machines. — Coalnjutting machines may bo divided into the following clas§es : — a. Heading machines, such aa the Stanley heading machiue. h. Disc machines, auch aa the Gillott k Copley machiaes. e. Chain machiiiea, auch ao the Jeflrey machine d. Bar machines, such as the Hurd machines. t. Percussive machJnea, such as the I ngeraoll -Sergeant machtnea. a. Heading UachineB. — This class of luachine has, up to the present, been used onlj to a ver; limited extent, the only machiue employed with Buccess in British mines being the Stanley heading It consists of an iron frame carried on two wheels set one in advance of the other. On this frame is fixed an engine with two cylinders placed vertically, the pistons being connected to the engine shaft by two cranku. This engine shaft carrier geared wheels at each end, and throngh these is geared to the principal cutting shaft. Fio. 99. —Stanley heading machine. which passes through the centre of the frame. On the end of this shaft a cross-head is fastened, to which are attached, at right angles, two cutter bars upon which are fixed the cutters. These cutters revolve in a circle, and cut out a circular core of coal about 5 ft. in diameter. The main shaft has a screw thread cut nearly its whole length, by which, aided by suitable gearing, the cutters are advanced. The cutter bare project about 3 ft beyond the croae-head ; and this length controls the depth of each cut. The machine is 'anchored' to the sides and floor, by means of screwed arms, U> maintain it in pusition, and to keep the cutters against the face. When a cut the length of the amis has been made, and the coal removt-d, the cutting motion is put out of gear, and the advancing motion put into gear, by which the whole machine is propelled forward ready to start a new cut. The whole machine, which is worked by compressed air, weighs between three and four tons. It can cut usually between 1 2 to 15 ft. in a shift of eight hours, including the time taken to bring down the coal and move the machine forward. Compared with band labour. 100 PRACTICAL COAL-MINING. the cost of cutting by tliis machine is high, but the great advantage of using it is tho rapidity with which a field of coal can be opened out. It can only be used in thick seams, i.e. seams above 5 ft. thick. b. Disc MacbineB. — There are now a coDKiderable number of different machines of this type used in British mines, but they are all constructed on practically the same principle, viz., that the under- cutting is done by means of a disc, on the periphery of which are lixed a number of picks or cutting tools, the disc working in the same way as a circular saw, but placed horizontally instead of vertically, and made to rotate by suitable gearing. These machines are enciusively used for longwall working, where they can be set to under-cut a long length of face in one operation. The Gillott & Copley is one of the best known types of disc machine, and has been successfully used for over twenty years. It is worked by compressed air, and has a frame about 5^ ft. long by 2J ft. wide, which carries two cylindera 8 or 9 in. dismet«r, and about the same length of stroke. The cutter-wheel, which varies Fio. 100.— The Gillott k Cujiley coal cutter, from 3 to 4 ft. in dianictcr, carries on its circumference about twenty-five steel teeth, and cut« to a depth of 3 to 3^ ft., the height of cut not being more than 3 in. This machine works at a low speed, the cuttcr-whcel making only about five or six revolutions per minute. Tlic machine nms along tlie face on rails, and is fitted with the usual wire rope and drum arrangement. The disadvantage of this machine is that it docs not cut level with the floor, the portion left on having to I>e taken up by hand. It can, however, be arranged to cut level, but it must Iw provided with a guard to keep the disc from taking the cuttings hack into the holing. Where the holing is done in the coal, this machine does very well, but is not so ethcient when cutting in fireclay as some of the other disc machines. Where the under-cnt only requires to 1>o about 3 ft. or so, this machine gives good results mider favourable conditions for working ; wlierc a deeper cut is required, some of the machines with larger discs, such as the Diamond machine, are generally used. The Higg it Meiklejohn machine is somewhat like the Gillott & Copley cutt«r, and holes the coal in the same way, the picks beiug COAL-CtrmNG BY MACHINBRT. 101 fixed into a circular disc. It is made bo that it can cut at the very bottom of the coal. The construction oF this machine will be under- stood by reference to fig, 101. It is placed on a steel frame xy, carried on four wheels, and kept in adjustment by screws at each corner. The two air cylinders d d are bolted to the frame, these cylinders being about 8 in. diameter and 10 in. stroke. A jib b, bolted to tlie side of the frame, carries the disc a, with eight or ten snugs ee, on which the picks are i>oltcd. A bevel pinion r, with twenty-seven teeth on the engine shaft, is geared into a circular rack/ of sixty teeth on the disc. The disc makes about sixty-two revolutions per minute, while the engine makes about 1 40 revolutions. The picks. Fio. 101. — Rigg h Msiklcjohn Toachiiie. 5 to 6 in. long, made of- hard steel, are in sets of four, and shaped so that the whole thickness of holing, about 4 in., is fidly occupied by the pick points. The disc revolves on a bearing, and is kept in position by a bottom plate, Inlted with stud bolts to the jib. The machine is reversible, and cuts either way. The engines are reversed by turning the eccentric pulleys round on the shaft, no links being used. The machine, whilst cutting, is hauled along by gearing from the main driving shaft, on which tliere is bolted a split worm which works into a pinion on the under shaft. The under shaft extends from the engine sole-plate to the front of the machine in which the bearings are seated. A solid wonn on the under shaft is geared into a pinion on the hauling sliaft, on which the drum or chain wheel g is placed. A gin. chain is coiled once or twice round the drum and 102 PBACnCAL COAL-MINING. is made fast to a prop 60 ft. ahead. The depth of cut is about 3 ft. to 3 ft. 6 in., the height of the macbiue 32 in., and the weight about IScwt. This is a very good machine, when compressed air is being used OB the motive power, for tbin ecams, as in cutting it makes its own floor. It is equally suitable for cutting in either a coal or fireclay holing, and has been extensively used with successful results at a large number of collieries for a good many ycara. The motive power used is compressed air, but it is now being constructed to work also with electricity. The Clarke &. Steavenson machine (fig. 101a) is constructed on much the same principle as the last two described, with the exception Flo. 101a. — Clarke & SteaveDMU mucliilie. of some minor details. Unlike the Gillott & Copley, or Uigg & Meiklejohii machines, it has been constructed to work with either compressed air or electricity as the motive power, the larger number now being made to be driven electrically. Two types of tliis machine are at present in use, the standard typo tor cutting in seams 26 in. and over, and the low type for cutting in seams under 26 in., the latter machines being capable of cutting iu scams 20 in. in height. The Clarke ife Steavenson machine, like those already described, is provided with a disc fitted with cutters which are alternately of the straight and forked type, or singles and doiibles, and are secured to the disc by being fitted into boies east on its periphery and held in position by cotter bolts and nuts, or by split pins. The number of cutters or teeth in the cutting wheel is twenty, of which ten are straight, or singles, and ten forked, or doubles. The discs used are either 4 ft. or 6 ft in diameter, according to the depth of the under- COAL-CUTTING BY MACHINKBT. 103 out required, the former making au under-cut of 3 ft. 6 in^ while the latter makes an under-cut 6 ft. 6 in. in depth. The standard type is 2 ft 2 in. in height, measuring from the top of the rail to the top of the easing, while in the special low type the height ia 1 ft. S in. In the Kigg it Meiklejobu machine tho cutter wheel is placed almost at the fnnit of the machiue, but in the Clarke Ji Steaveneoii it is placed at the roar, which ia a great advanh^, as the material from the cut m delivered at a jwiiit close 104 PKACTICAL COAL-MINING. k) the driver. As a consequence, if the machine is working beyond its capacity and is hard pressed, the driver can materially assist it by clearing back the cuttings from the wheel. This at first was considered a disadvantage, as it was thought that it would prevent the machine from cutting forward and backwards if required, but it has been found that by changing the cutters in the disc (i.e. putting in cutters suitable for the direction in which the machine is to travel) the machine can cut back equally as well as forward. At the same time that the cutters are changed the long bridle must also be changed to the other end, and the haulage rope drawn through under the machine. The Clarke & Steavenson machine was first introduced about ten years ago, and since then it has proved to be a good all-round coal-cutter for working under very various conditions. The Diamond machine (fig. 101b) is another well-known machine of the rotary disc type. A large number of these machines arc at work in the Midland coal-fields, and have been found to give good results in seams where a deep under-cut is required. The Diamond Ck)al-Cutter Company, who matmfacture the machine, were the first to introduce deep under-cutting, the depth of the under-cut varying from 4^ to 6 J ft., the latter depth of cut being employed in seams of medium thickness, e.//., 4 to 5 ft. Diamond machines are also made to cut in thin seams of 2 ft. and under, with an under-cut of 3 to 3^ ft., as is usual in such seams. Two types of this machine are now con- structed, those fitted with cylinders to work with compressed air, and those fitted with motors to work with electricity. Several new features have been introduced into these machines. In the com- pressed air machines the power-cyliiidei*s, instead of being placed side by side at one end of the machine, as is the usual practice in the other disc cutters described, are placed one at each end o^ the machine, an arrangement which has an important effect in assisting to balance the large cutter-wheel. This arrangement also decreases the width of the machine, which is a point of no small importance, especially where cutting with machinery has to be done in seams with a bad roof. Another feature of this machine is that by fitting on an extra pair of axles and wheels and turning the machine over, it can be made to cut at any height in tlie seam, and it can cut in either direction. The cutting wheel, which is of the usual disc pattern, is attached to a strong bracket fixed to the framework of the machine. The Anderson-Boy es machine (fig. 101c) is another of the longwall machines of the disc type, which has recently been put on the market by the firm of Messrs Anderson, Boyes & Company, of Motherwell, N.B. The machine, which is electrically driven, has been mainly designed by Mr Daniel Burns, M.E., who has had a large practical experience in the installation of coal-cutting plant in Scotch collieries, especially thin seam collieries, and the design of the machine is the outcome of that experience, the improvements which he has intro- COAL-CUTTINO BY HACHINERT. 106 duced being suggested by the derects in other coal-cutters which are now at work in our coal-fields. Of course, every machine has some imperfections, and the ideal machine to work under varying conditions is as yet in the experimental stf^e. The following is a description of the machine ; — The frame, which is of heavy angle steel 4J in. by 4^ in. by 1 in., extends along each side, and is braced by the motor box at one end and the switch box at the other, both being attached to the frame by heavy fitted bolts. The cutter wheel is 4 ft. 6 in. in diameter, and carries twenty cutters, ten doubles and ten singles. The peripheral speed of the cutting wheel is about 300 ft. per minute, and the reduction gear is carried on three shafts. In otder to keep the pinions closely in gear the plummer blocks are all cost in one piece, the arrangement of the gearing for the cutter wheel being such as admits of the use of a Fio. lOIc. — AnderBoii'BDjes machinr. short stiff bracket which carries the wheel and arc-plate. The haul- age gear is fitt4xi low down in the body of the machine just behind the switch box, and is arranged so as to take the rope upon the under side, whether the machine is cutting back or forward. An arrange- ment is fitted to the ratchet wheel which admits of the feed being thrown off or regulated while the machine is running. This is fixed in a position which is easily accessible to the person driving the machine, and is an appliance which should save a great deal of time where the cutting has to be done in under-clay that varies much in hardness. The most important part about the machine is the motor, which is specially constructed for the work, and is of much greater power than thoee most commonly used in coal-cutters, being 39 horse- power if the machine is series wound, the class of winding most generally used for coal-cutters ; if shunt wound it gives 38 horse- power. 106 PRACTICAL COAL-MINING. The Jeffrey machine is an American type of disc machine which has only recently been introduced into this country. It is con- structed in two types, viz., to be driven by compressed air and to be operated by electricity. The construction of both types are nearly similar, in the latter a motor being substituted for the air cylinders. The electrical machine consists chiefly of two parts, the motor and feeding gear on its frame, and the cutting wheel. The frame of the machine is of the usual rectangular shape, and made of steel, with the haulage drum for moving it along the face placed at the forward end. The motor is placed in the middle of the frame, and the cutting wheel is placed at the extreme rear end. By means of a hand wheel the disc can be tilted up or down so as to follow any unevenness in the floor, or pass any obstruction in the holing, such as ironstone balls, which may be encountered. A device is also provided for altering the speed of travel of the machine without changing the speed of the cutter wheel. Another novelty in connection with this machine is that it only requires a single rail to run on, this rail being placed under the centre of the machine, the side thrust being taken up by special sleepers and light screw-jacks. The machine is operated from the front end, the feed being driven by an eccentric through a ratchet and pawl on to the haulage drum, and there is an arrangement for enabling the feed to be stopped, started, or adjusted without it being necessary to stop the motor. This enables the machine to clear itself should it get hampered by a fall of coal. Three rates of cutting are provided for — 8, 16, and 25 inches per minute, or vice versdy should such lowering of speed be required, according to whether the under-cut is soft or hard. The machine is constructed to cut either forwards or backwards, making it suitable for working in a short length of face. The high-speed wheels gearing the arma- ture down to the cutting wheel and feed eccentric are enclosed in a casing arranged so as to run in oil, which reduces the noise of the machinery while cutting is being done, and so enabling the attendants to hear any movements in the coal or roof more readily. The cutters, which are all singles, are secured in position by suitable boxes on the periphery of the wheel. One half of the cutters are set with their faces upwards, and the other half downwards. Different sizes of cutting wheels are used according to the depth of under-cut required, the smallest size cutting 3 ft. 6 in., and the largest cutting 6 ft. under, the height of the cut being 4 to 6 in., according to depth. The electric machine is fitted with a 25 horse- power motor, and weighs about 34 cwt., the principal dimensions being 8 ft. 2 in. long, 3 ft. 8^ in. wide, and 19 in. high from the top of the rail. Chain Machines. — These machines arc of comparatively recent date, having been first introduced into American mines in 1894, but since that time they have rapidly made their way into a large number of mines in the United States. Only in a few instances have they been used in Great Britain. COAL-CUTTING BY MACHINERY. 107 They are moet largely employed for cutting ii) narrow work, i.e. iu pillar and stall workings, although machines like the Morgan- Gardner are suited for longwall work. The principle of the chain machine \a almost that of the band-saw, with the addition of suitable mcchanisDi for movhig the machine while it is cutting, The machine oonsistB of three principal parts : — (a) A tixed carriage which can be clamped fast to the side af the working place by screw-claws, the cut being effected laterally, the claw holding the carriage in front being set at an angle of 45° so as to take up the thrust ; {li) a movable frame in the shape of a trapezium that rolls longitudinally on the carriage, the short l>ase of which carries the motor, while the long base is in contact with tbc face, having over its whole periphery a groove through which passes the endless chain ; (r) the endless ciiain, moving in the groove of the frame, passing at the back round a driving pinion, and in front over two small guide pulleys. The cutters, which are often set upwards and downwards alternately, are Fio. 102. — JclTrey cliain macliiiie. fitted to the links of this cliain. Nearly all of these chain maohines are now driven by electricity. The Jeffrey chain machine (Hg. 103) is designed to work either in pillar and stall or longwall workings, and can be built to work by compressed air or electricity. It consists of three principal parts, the l>ed frame, the sliding chain cutter frame, and the motor carriage. Upon the frame arc mounted the feed racks and a cross-bar on which rests the jack for taking the backward tlinist. The cutter frame consists of one steel centre rail, the cutter bead, and two side guides for the cutter chain. The cutter frame is triangular in shape, making it necessary to use only three wheels, two in the cutter head and the sprocket wheel, for conveyhig power to the cutter chain. The driving and feeding mechanism, consisting of steel pinions and wheels for working the machine, are momited on the carrit^e. The cutter bits, which are Rxed in the ends of the cast steel cutter links, arc straight, with a slight hook at the cutting end. When it is set working, the chain begins to travel round, while at the same time tbc cutter head and frame are advanced into the coal. The machine 108 PRACTIOAL COAL-MINING. having out to the full depth, the direction of travel is reversed and the cutter frame drawn in again. The machine is then slid along a distance about equal to that of the cutter head, and the work proceeds as before. The machines are built to under-cut 5^ and' 7 ft., the height of cut being 4 to 5 in. Two types of the Jeffrey machine are constructed, the ordinary type for working in moderately thick seams, and the low type con- structed for operating in thin seams. The construction of both machines is practically alike, the only difference being that in the low type the motor is set much lower down in the carrying frame, which reduces its height. Another type of the chain machine is the Morgan-Gardner, which in construction resembles very much that of the Jeffrey machine, with the exception of some minor details, and so does not require further description. Another machine of the chain type which has been recently intro- duced is that known as the Mather & Piatt machine, manufactured by the well-known firm of that name at Manchester. The construction of this machine is much on the same lines as those just described. Chain Shearing Machine, — This type of machine is used for shearing or side-cutting the coal in narrow places, such as in pillar and stall working. The construction of the machine is somewhat like the chain under-cutting machhic, but with the frame round which the cutter chain passes placed in a vertical instead of a horizontal position. The outside frame is constructed of heavy steel angles with the flanges turned in, which gives a broad w^earing surface for the carriage that carries the motor and gearing. The machine is fitted with a motor at the rear end of the machine which drives the shearing chain through spur and bevel gearing. Bar Marlines, — This is a type of machine which is very different— - so far as the tool used for under-cutting is concerned — from the two classes of machines just described. Instead of the under-cutting being done by a disc or moving chain, a circular tapered steel bar with a number of teeth or cutters fixed in its periphery is employed to do the cutting. For under-cutting in certain seams this type of machine has some advantages over the disc cutter. In seams which are soft and friable, if disc machines are employed a good deal of trouble is often experienced by the under-cut coal coming down on the disc before it can clear itself, or before sprags or holing props can be put in to support the cut coal. The larger the disc used, the more likely is there to be trouble from this cause, as the area of under-cut and unsupported coal will vary as the diameter of the cutting wheel. These falls of coal taking place on the disc cause delay, as the machine requires to be stopped mitil the fallen coal is cleared away ; and where cutting is being done in thin scams with a bad roof where propping is carried close to the machine, the clearing of such coal is often a tedious and difficult process. Where such conditions prevail, the bar machine may COAL-COTTINQ BT MACHINERY. 109 be employed with good resulte, hs only a small area is under-cut and left unsupported for a very short time, as the spragging can be done quite close to the cutter bar. Another advant^e that is claimed for this type of machine is that less power is required to drive it than a disc or chain machine for an equal depth of under-cut. In actual working practice we do not think there is a very great difference in the power required for driving the two classes of machines, and it is a point on which at present too much value need not be put, for the power required for driving is after all not of so much importance aa the time required to cut a. given area by a machine. Other advantages claimed for the bar machine are that there are no bearings under the coal when cutting is proceeding, as in the centre of a cutting disc ; that the mocbinemeu are not so hard worked as Flo. IDJa.— Hurd machine (under tjpe). with disc machines ; thAt the holinga are better cleared out ; and that the cutters are easier eiamined. The Hurd bar machine (figs. 102a, 102d) is the best known machine of the bar type. It has been installed at a considerable number of collieries in England and Scotland, but ita numbers are limited compared with the number of disc machines which are now in operation. The Goolden bar machine is practically similar to the Hurd in its general arrangements, with some differences in detail. In the Hurd machine the cutter-bar has a reciprocating aa well as a circular motion, which produces a chipping as well as a cutting action, while in the Goolden machine the bar has only the circular motion. Perciieeive. Maehinen.—The percussive machine, as its name implies, under-cuts the coal by a series of blows in much the same way as a 110 PRACTICAL COAL-MINING. miner would under-cut with his pick, so that their action ia altogether different from the machinex previously described in which the under- cuttiug is done by a continnously rotating disc, chain, or bar. Per^ cussivo machines arc, therefore, practically pneumatic or electric picks. They resemble mechanical rock-drilla in that they are only furnished with a single cutting bit, thongh they differ from them in having no mechanism For rotating nor a screw for giving tbe feed, while, instead of being fixed at work, they are esaeutially movable, Thcae machines were first introduced into Araericnu mines about 1880, and since then they have bocTi extensively employed for mechani- cal cutting in the coal mines of the United States and Canada. In quite a targe number of the mines in those countries the luider'Cutting is cutirely performed by percussive cutters, although in some districts they are being gradually displaced by the chain machine. Up till the present they have been very little used in British mines, the other Fic. 102b.— Hurd machine (over type). types of machines being preferred. The American coal-seams are more suitable for cutting by percussive machines, being of a softer and more triable nature thati the coal-seams of Great Britain. All percussive machines arc of one type and are worked on a similar prin- ciple, though differing somewhat in detail from each other. They are constructed with the following main parts * :— (a) A cyliiidfT 3 to 4 in. diameter and S to 12 in. stroke. (b) A piston and rod, witii tlie rod extended to make the cutting tool. (-:) A valve and valve-chest, the valve being thrown bj air, or oiKrated by a small iiidejiendent engine, cushioning nrrangenienta being in all cases a necessity. (rf) A BleevB or guide attached Lo the front end of the cylinder, l» guide Kiid steady the piston-rod, and also {jrovided with arrangements for pre- venting the piston and cutting tool from tumine. ((} A Buitoblc |rick or cutter, usually shari'ened to a fisli tail shai-e, (f) A pair of plain wheels upon which the machine is carried, the wheels being placed so as to balance the machine. (if) A jiair of handles at the bacV for the macliineman lo take hold of. ■ HHgintering H'lya^i-He, August 1903, p. 12i. COAL-CUTTING BY MACHINERY. Ill Method of Working Pei'cumve Macliines, — "In operating a pick machine the runner sits on a board or platform, inclined to the face of the coal ; one foot of the operator is braced against one wheel of the machine, and with the two handles he directs it against the coal, picking off the coal exactly as a miner would do, except with much more force to each blow. The under-cut made is V'^^P^i 13 to 18 in. in height at the face, and tapering back to a feather edge on the floor at the rear of the cut, the depth of the cut being from 3 to 6 ft. deep, according to the thickness of the coal. A helper shovels away the cuttings as the machine, guided by its operator, loosens the coal in the under-cut." * The work in operating these machines is severe, especially with unskilled machinemen and in hard coal, for the inclined board and the chock provided by the operator's foot only partially takes up the lecoil of the machine. In a hard seam, unless the machineman can rest frequently, the labour of keeping the machine up to its work becomes veiy fatiguing, in fact almost unendurable, and hence, as already stated, they are best suited for cutting in soft and friable seams. There are now quite a number of these machines in use, but we need only describe one or two, as they are all so much alike. The Ingersoll-Sergeant machine (as also the Harrison machuie) is fitted for working in narrow " rooms " or drifts. It is simply a chisel attached to the continuation of the piston-rod of an air cylinder, and may be called a slotting machine. The machine (fig. 103) is mounted on a pair of wheels to enable the cutting tool to operate in any direction, either under-cutting or cutting in an upward direction, and to facili- tate the removal of the machine from point to point. The tool receives a reciprocating motion from a small cylinder of the usual type fixed to the frame of the machine. The piston works through suitable packing at the front end of the cylinder, and is made long enough to project beyond the end of the sleeve in which it works when at the end of its back stroke. At the forward end of the cylinder is placed a buffer of leather of such construction as to form a cushion for the piston. The projecting part of the piston-rod is tapered so as to fit a corresponding taper in an extension piece which is fixed to the piston rod by a key. The outer end of this extension piece is made to receive the pick or chisel, which is also held in position by another key. The piston-rod is provided with eight straight grooves engaging in similar projec^tions in the end bushing for the purpose of preventing any accidental movement of the piston and pick. The cutting edge of the pick is shaped like a V) having a sharp edge and cutting points. The pick can be easily removed and sharpened. The machine, as already described, is worked from an inclined board of convenient size, while making an open channel under the coal of 4 ft. to 5 ft of face and 3 ft. to 5 ft. of under-cut. The claims of * Mines and Minerals^ June 1903, p. 510. 112 PRACTICAL COAL-MININO. this machine are that it ia Bmall, simple in construction, requires little space, is light — weighing only about 750 lbs. — portable and The Harrison machine is very similar to the lugersoll-Sergeant, but is somewhat heavier and stronger. The air distribution is effected by a small ausiliaiy motor, which cute off a half-stroke, and the Fio. 103.— Iiiftersull-Srrgeaiit inAchiu«. cylinder head is protected by a leather cushion, which deadens the blow of the piston when the bit or cutter does not strike the coal. With an air pressure of 70 lbs. per square inch this machine gives 190 to 310 blows per minute, witli a stroke of 1 1 in. It makes an under- cut of 6 ft. deep and about 6 in. in height. The fjullivan machine, which is also driven by compressed air, has a system of variable expansion that permits of graduating the l)low, and the cylinder head is protected by an air-cushion. It greatly COAL-CUTTING BY MACHINERY. 113 resembles an ordinary rock drill, is mounted on a carriage nmning on rails, and the bit, much longer than usual, is supported by an arm that also acta as a guide. This appliance can be moved in a vertical plane so as to make a cut in the face for its whole height ; and the forward feed is given by a small winch on which a chain is wound, so that a cut 6 in. wide can be made to a depth of 7i ft. The Morgan-Gardner percussive machine, unlike the three above described, is driven by electricity, and is practically the first of its class which has been successfully worked by electrical power. The construction of the machine is practically similar to those just described, with the exception that an electric motor is substituted for a compressed air cylinder. The rod with the cutter attached is drawn backwards by a cam during half a revolution, and then a strong spring propels it sharply forward, the cam being worked by gear from a continuous current motor with vertical axis carried on the machine. It can give from 175 to 225 blows per minute, and cuts to a depth of 4^ ft. The weight of the machine is about 750 lbs., and it has a total length over all of 7 ft. The Champion machine is also of the percussive type, but differs very considerably in construction from those just described. It is practically a combination of the percussive machine and rock drill. The machine consists of five essential parts, viz. : (1), The support- ing column (5 ft. long), 200 lbs. ; (2), the segment with accessories, 114 lbs.; (3) the air drill, 239 lbs.; (4), extension rods, two, for cutting up to 7 ft. deep, 28 lbs. ; (5) the bit. The supporting column, of simple construction, is securely fixed about 3 ft. from the working face. Sliding on this column longitudinally is a sleeve which can be fastened at any given height of the support. In a bearing of the sleeve the toothed segment is carried, and may be rocked therein from a horizontal to a vertical plane, or to any intermediate position. Pivoting in the hub of the segment and in its axis is a connecting piece commanded by a worm acting on the teeth of the segment ; a handle driving the worm may be attached to either end of its axis. The drill machine is securely fastened to this connecting piece, and can therefore be swung in a plane parallel to the segment by turning the handle of the worm ; if, therefore, the segment is attached horizontally, the machine will act as a coal cutter ; if vertically, as a coal shearer ; if at an angle, the machine will cut into the coal at that angle. It will thus be seen that the machine can make a cut at any given height and at any given angle. It can also be used as an ordinary rock drill, and this simply by not turning the handle commanding the worm. The working of the machine is controlled by one man, who with one hand turning the handle of the worm produces a swinging action of the drill, while with the other hand he regulates the advance of the drill into the coal by turning, as in any ordinary rock drill. When the 8 114 PRACTICAL COAL-MINING. drill is set to work, the cutting-bit strikes the coal at the rate of about 350 blows per minute. It would penetrate very fast into the coal were the blows directed to one place only ; but, while the machine is at work, the cutting-bit is gradually displaced in a plane parallel to the segment, by turning the handle of the worm ; and the cutting-bit therefore strikes every blow in close proximity to the preceding one. It desciibes an arc having for its centre the axis of the segment, and the outcome of this motion is an even cut. When the cutting-bit has reached the end of an arc, the drill is advanced to the extent it has been cutting into the coal by turning the feed screw, and the motion given to the worm is then reversed. Percussive machines are best suited for thick seams with a good roof, as they require a clear space of 7 to 9 ft. In the American mines their use is almost exclusively applied to narrow work in pillar and stall workings, but they could also be usefully applied in conjunction with longwall machines in cutting the narrow work which is necessary to allow most disc machines to start work, this narrow work having at present to be done by hand labour. Ohoioe of Machine. — If the owners or managers of a mine deter- mine upon adopting mechanical cutting, the first question which will naturally arise is, what type and class of coal-cutting machine should be used for the work to be done ? This is not so simple a question as it looks, and cannot be answered right off-hand. The choice of machine will depend upon various circumstances, such as — (1) The mode of working at the mine ; (2) the nature of the holing ; (3) the position of the holing, i.e. whether the holing is to be done at the bottom, centre, or top of the scam ; (4) the thickness of the seam ; (5) the nature of the floor and roof. If the mode of working is longwall, which is most usual in this country where coal-cutting is done by machinery, then the selection of a machine must be made from the disc, bar, or chain classes of coal-cutters. We have already stated that by far the larger number of machines used in British mines are of the disc type, and under ordinary conditions this seems to be the type most suittible, but, as already pointed out, there are certain kinds of seams in which it would be possibly better to adopt the bar machine, e.eed at which it works, a large amount of power can be applied from quite a small pulley by belting. It does away with the danger of ropes or pipes in the shaft, and avoids the complication of pullevs and ropes at the pit-head and pit-bottom. The cables can be readily fixed and taken round curves ; there are no jointe to be affected (as in pipes) by vibrations or shocks, and the space occu- pied by conductors is very small. The surface plant can be placed any distance from the shaft and not neces- sarily in line with the latter. Higher efficiency can be obtained than with compressed air or steam when used underground. Disadvantages : — The danger of fire, either igniting fire-damp or setting fire to screen-cloth or brattice-wood, owing to sparking at the motor or ' short>circuiting ' in the cables. Electric machinery is easily damaged and thrown out of order, and often requires skilled men to reiMiir it Ite unsuitability in damp and dirty workings, as the cables and beltings soon suffer injury under such conditions. The first cost is much higher than for ordinary haulage engines driven by steam. TRANSMISSION OF POWER. 135 The following table shows the comparison in the cost of transmitting power by the various systems in U8e * : — System employed. Electricity, . Water pressure, Compressed air, Ropes, Electricity, . Water pressure, Compressed air. Ropes, 330 1640 ft ft. Pence. Pence. 1-80 1-84 2-27 2-»6 317 3-23 1-26 1-49 0-46 0-48 0*46 0-55 0-72 0-80 0-25 0-27 3280 ft. Pence. { 1-94 ! 2-61 3-33 1-58 0-53 0*62 0-84 0*30 16,400 fL Pence. 2-27 4*03 4-05 2-88 0-62 1-33 1*21 0-80 65,250 ft. Motor. Pence. X 4-61 ^ 9-57 CO 6-89 12-68 J 1-15 J "^ 8-54 (g 3 36 1 'O 3-39 ) >» W The cost as given above is for the transmission of 100 horse-power for the distance tabulated, from which it would seem that transmission by wire ropes is the cheaper up to 3000 ft., and electricity for longek- distances. Electrical Terms, — ^The volume of an electrical current is measured in amperes in the same way as the speed of air in pipes is measured in cubic feet per minute or second, or that of water in gallons or feet per second. The tension or pressure of an electrical current is measured in volts, and corresponds to the measurement of steam pressure by pounds per square inch. An electrical horse-power equals 746 watts, a watt being the power conveyed by a current of one ampere at a pressure of one volt in a second of time ; or, in other words, when a current of one ampere passes through a resistance of one ohm in one second. The resistance of any conductor to the passage of electricity is measured in ohms. The difference of pressure of electrical energy at varying points is usually spoken of as electromotive force (written E.M.F.), and is measured in volts. Let E=: electromotive force in volts, R = resistance in ohms, C=the current in coulombs, thenE=RxOorC=§ Work done in mechanics is usually measured in foot lbs. In electricity, however, the watt is the unit of work ( = volt x amp.) H.P. in m«c*»*ni<»=^3^^(JJ^ =746 watts. ti T» • 1 *-: J* watts volts X amperes. H.P. m electricity = -^^= j;^^ * Trans. Intl. Civil En^, 136 PRACTICAL COAL-MINING. Power given out by a current of 1 ampere at a tension of 1 volt = 1 watt ,, ,, ,, 2 amperes ,, ,, 2 volts = 4 watts 10 2 = 20 }i 1} »» *" »» »» II ^11 '" II 74-6 „ „ „ 10 „ =746 ,. =1H.P. 7-46 „ „ ,. 100 „ =746 ., =1 H.P. That is, a current of 74*6 amperes at a tension of ten volts, or one of 7 '46 amperes at a tension of 100 volts, is equal to one electrical horse-power. A wire of a given size will permit the flow of a given number of amperes proportional to its diameter. For instance, a conductor of 19 wires, each wire being 16 B.W.G., is suitable for the flow of about 50 amperes for a distance of 1000 yds., with a loss in the conductor of, roughly, 10 per cent. If the voltage of the above 500 X 50 current be 500, then the horse-power will be= — ^.^ — = 33*5. 746 For large current and small pressure or voltage, large conductors must be used, which are expensive. For small current and high volt- age small conductors may, however, be employed, which is more economical, although they increase the danger arising fi*om sparking, short circuits, etc. For underground work voltages exceeding 500 are rarely used, owing to the danger of sparking and of shock to men coming in contact with the cables. For electric lighting with incan- descent lamps, a voltage of 50 to 100 volts is usually employed. An incandescent lamp of 20 candle-power at 100 volts takes about 0'6 ampere, i.e, 100 x -6 = 60 watts, or 3 watts per candle-power.* * For further details of the application of electrical power in mines the reader is referred to Electrical Practice in Collieries^ by Daniel Burns, M.InstM.K. London, second edition, 1905. GHAPTEB Vm. MODES OF WORKING. Choice of Methods. — The main object in any Bjstem of working is to extract as much of the coal as possible, with the maximura of economy and safety, and in longwall, the coal left in ought not to exceed 5 per cent, to 7 per cent, of the total quantity in the seam. The two principal methods of working are pillar and stall (stoop and room in Scotland), and longwall, all other systems being simply modifications or combinations of these two.. The method of working any seam naturally depends on local circumstances in each individual colliery, and, speaking generally, varies according to the thickness of the coal. Seams of 4 ft. and upwards are usually worked by pillar and stall ; seams having a thickness of less than 4 ft. are usually worked by longwall. There are, however, exceptions to this rule. Besides the thickness of the seam, the mode of working will depend on other circumstances, such as — The inclination of the strata and the nature of roof and pavement. The depth of the seam from the surface. The chemical and physical proiwrties of the coal. The natural cleavage of the coal and that of the rocks forming the roof. The presence or absence of water. The ^icinitv of other seams or of other workings which should not be interferea with. The number of dykes and dislocations in the field to be worked. Longwall. — In this system the whole of the mineral is usually extracted in one operation. In some cases a modification of the system is adopted, and pillars are left along the main haulage roads to help to maintain them, but it is very doubtful if this is an advantage, as it generally entails the loss of a large percentage of coal, which might otherwise have been got, and, as far as the security of the road is concerned, it would seem, from recent investigation, to do more harm than good. To work a seam to the best advantage by this method, there must be— A fairly good roof and |)arement. The roof and lavement should be free from water. The seam must be neither too thick nor too highly inclined. The ooal itself should neither be too soft nor t» "'""'? ™'?"<^' » « groat many accidents from falls of coal arc due to the neglect of using holing props (see C. M. K. Act as to rules for spragging the coal). By properly apragging the coal a lai^cr amount of round is obtained and a smaller percentage of dross than when this precaution is neglected. In some districts where longwall is practised, the walls are made as lung as possible, 25 to 60 or even 70 yds., and a road laid along the face to take in the tultH. This is a decided advantage where a large area of coal can Iw opened out, as it saves cxi«nditure for ripping, and few roads require to he kept open for a given length of face. MODES OF WOBKING. 141 In the ' Top Hard ' seam at Nottingham, of which a section is given, fig. 108, the method of working is longwall, tbo walls Iteing 25 to 30 yds. in length. The 'holing' m done in the soft blaes,* and sprags are put in every 6 ft. The places are worked on 'end,' and no blasting is required ; when it is worked on ' plane ' the coal is more crushed. The rubbish from the waits and ripping is sufficient to pack the whole of the waste, and a pack is put in when there is 4 ft. of ripping available. Two rows of wood, 6 in. diameter, are kept between the pack and the coal, the back row props being placed at a distance of not more than 6 ft. apart. The tram road is laid between these two rows of props (tig. 109). The coal having been holod, the whole length of the wall and the raits are lifted, a ' cut ' is taken simultaneously right and left along the wall, the rails being laid down anew from ei^er aide at the same time, and a new pack of 5 ft. is put in (at X). The props of the back row are drawn and set up at the face again. Fid. 109. — Plaa of wall ahowiug tram road. The branch roads are cut off every 50 fms. by new slopes, and the top coal is taken down by these roads. In the main roads the 6^ ft. of shale is also taken down, a good liigh road resulting. The output per man averages four tons per day. In the Main seam at the same colliery the working is similar, but the walls here are 60 yds. long, and the seam is worked on 'end' us before, no blasting being required. The under coal and fireclay are holed to a depth of 5 or 6 ft., and sprags put in. The rubbish got from ripping and holing is not sulhcicnt to fill the whole of the goaf, and packs 6 ft. thick and 9 ft. apart arc put in at intervals along the wall, while two, and sometimes three, rows of props of 6 in. or 8 in. diameter wood are set up, 6 ft. apart, with a distance of 3 ft. between the rows ; the back props being drawn and * ArgHUceous ah»\v. 142 PRACTICAL COAL-MINING. shifted forward as packing proceeds. The tubs are taken along the face between the inner row of props and the coal. Where the roof is tender, straps composed of old rails are put up between the coal and the props in the nearest row, the inner end being wedged into the coal. The * Drumgraj ' seam in Lanarkshire varies in thickness from 1^ ft. to 2^ ft., and is worked long wall. The seam in some districts lies very level, and the general mode of working is to set off roads in the direction of the rise and drive branches, right and left, the walls being 15 to 20 yds. long. The coal is hauled by boys along the face in small bogies to the ' road-head,' and there fillod into the tubs. The roads are ripped to a height of 5 or 5^ ft., and made 7^ ft. wide, the rubbish got from the ripping and holing being suffi- cient to pack the whole of the goaf. The ripping of the roads costs 78. 6d. to 10s. 6d. per fathom, and frequent repairs are necessary to keep them in order. At Westrigg Colliery, near Bathgate, the Drumgray seam is only 14 to 17 in. thick, with a hard rock roof. It lies flat and- does not contain much water, although the other seams at this colliery are very wet. Owing to the roof being strong, very little timber is required, but the roads soon get very low. The holing is done in the coal, the floor being hard shale. Each man keeps his own place in order, and does the ripping of his own road, the price paid in 1898 being about 4s. per ton of coal got. This price includes the ripping of r^udB and the drawing of the coal. The output per working place is about three tons per shift of nine hours. To work so thin a seam would be almost an impossibility with a bad roof, as the cost of upkeep would be too great; but, in this instance, very little extra expenditure is required, the fireman alone being generally able to examine and keep fifteen to twenty places going without much trouble. Sand or Water Pack, — In British mines where seams are worked on the pillar and stall system, it is not usual to pack the waste ground when the pillars are extracted, the timber being usually withdrawn and the roof allowed to collapse. If the seam is thick and situated at no great depth much damage may be done to the surface when the pillars are extracted, especially in the vicinity of towns, where the buildings may be partially wrecked, of which many instances have occurred throughout Britain. To obviate this the goaf may be packed with sand or fine debris run in with water through a series of bore- holes from the surface. This process was first introduced in America in connection with the working of the thick anthracite seams, which in many places lie at no great depth from the surface. The practice there is to utilise the fine refuse and sludge from the screening and coal- washing plant, which is sluiced with water into the waste workings. The system has also been successfully applied in Germany, where in some districts, such as Silesia, thick seams, 20 to 30 ft., have to* be worked, and where previous to the introduction of the sand>pack a large quantity of the coal was lost in the removal of the pillars. MODES OF WORKING. 143 and much damage done to the surface. The chief material used for this purpose in the Silesian mines is sand, although other material, such as coal-dust, cinders, clay, refuse from coal washcries, ground stones and bricks, are also used. The fine debris is carried down the shafts in pipes, and thence to the required position in the workings, by a stream of water, the water being allowed to filter through the pack and then pumped to the surface. " At the space to be packed under- ground, the delivery pipe is raised as close to the roof as practicable at the upper end of the open space, and the openings, except that for the delivery pipe, are closed by dams. Water alone is then allowed to flow through the pipes for some time so as to clear them thoroughly, and afterwards the tipping of the material into them, which is done through a funnel, is commenced. The water, after depositing its load, filters away through a dam placed at the bottom end of the pillar, eventually reaching clearing tanks, whence it is pimiped to the surface. Meanwhile the material is gradually depositing and being tightened by its own weight, until only the small space round the mouth of the delivery pipe remains unfilled ; the flow is then turned off in this direction, and the same operation repeated with it by means of branch pipes somewhere else. It is advisable to have telephonic commimication between the tipping and delivery ends of the pipes. After giving the packing a day or two to dry, the dams are removed, and the coal in the neighbourhood can be worked : the packing remains quite tight and firm, and resembles a natural stratified bed.'^'**^ The cost at one colliery in Germany for packing the waste in this way was about 6d. per ton of coal won, this including the cost of pumping, pipes, interest on capital — everything, in fact, except the sand and i^ater, which were got free. There are few districts in Britain where sand could be had free in sufficient quantities to carry out this system successfully, but at many collieries there are large heaps of refuse which might be utilised for the purpose. The principal advantages claimed for this method of packing are : (a) a larger quantity of coal can be won ; {b) little damage is done to the surface ; (c) less timber is required. To secure success in working longwall it is necessary that — The places or walls should be kept going regularly, and fully equipped with the full complement of men, otherwise some of the places will fall behind and wul cause trouble with the ventilation, and in other ways. The line of face should be kept as even as possible, and unless the seam is very highly inclined, not worked zigzag, as the point or ' nose ' is sure to get crushed, the ' ribside ' will not have sufficient weight, and very often the wall will get closed at this point altogether, hindering ventilation and causing trouble and expense in ' winning-out * again. No portion of the face should be in advance of the rest further than a sinele ' cut,' as this makes the coal more difficult to get, and more dross (' slack ') will be made by the increased ' shearing ' and ' holing.* The places should be carefully propped, while no tunber should oe left in * Trans. I. M, £ngii., voLxxviii. p. 825. 144 PRACTICAL COAL-MINING. the waste that can be avoided, as it keeps the roof from subsiding properly, besides increasing timber costs. The holed coal ought to be carefully spragged by holing props or 'gibs,* to get the full benefit of the weight when it comes on. The ripping in each road should always be kept well forward and the builoings (packs) well and tightly laid. If they are loose, much trouble is often caused by their being pushed out into the roads when the weight comes on them. Advantages of LrmywalL — The advantages to be derived from working any seam by longwall may be briefly stated thus : — The coal is generally extracted with only 5 per cent, to 7^ per cent, loss, resulting from places 'closing' and requiring ribs of coal left in, and from bottom pillars required. As the ' shearing ' is confined to one or two places or main roads, there is a considerable saving in that part of the work, and, therefore, better coal at lower cost is obtainable than where much shearing is required. The coal is easier to work, and the working price is cheaper, as a rule, than in bord and pillar. The ' weight ' often reduces the labour of getting the coal, for, if properly taken advantage of, it helps to bring down the coal after being ' holed,' thus saving expense in blasting and giving from 10 to 15 per cent, more round coal than pillar and stall working. £ase in ventilation, small cost for bratticing, and com^iaratively short dis- tance for haulage for a nven output. More men can be emploved in a given area, and, therefore, a larger output can be got than in pillar and stall working. Fewer roiSs require to be kept open for a given output, and there is a con- sequent saving in rails, sleepers, timber, etc. With thin seams and where the conditions are suitable, coal -cutting machines can be used. The disadvantages are : — The roads are more difficult to keen open than in pillar and stall, especially if the roof and floor are wet, ana the latter tendB to creep. * Unless the work proceeds re^larly, roads and faces are difficult to keep open, and the ventilation is hinaered. Dykes and dislocations arc more difficult to deal with than in pillar and stall working, and cause much trouble with the roof and sides. Longwall working is unsuitable for thick seams with little rubbish available for packs in the wall. It would seem from the Inspectors of Mines' Reports that there is practically no difference between longwall and pillar and stall, so far as safety and the number of accidents arc concerned. Pillar and Stall, Bord and Pillar, or Stoop and Boom. — This mode of working, with its numerous modifications, may be said to be the only other method of working a seam unsuitable for longwall. Seams from 4 ft. thick and upwards may be worked by pillar and stall, and some even thinner than 3 ft., where the pavement is soft * The word * creep' is usually confined to the slow rising of floors, which sometimes, owing to the pressure of the walls on either side, become more and more convex, ana sometimes even block up the road or render it impassable. MODES OF WORKING. 145 fireclay, a portion being lifted, as in some districts of Cumberland. If a seam situated below another working containing water has to be worked, it is often the best method to adopt, no matter what thickness the seam may be. The system, however, is best suited for thick or moderately thick seams, with no available debris. In seams of a soft or friable nature with a rock roof it is likewise, as a rule, the best method of working. Pillar and stall working is divided into two distinct operations : Driving places in the solid coal, and dividing the area of ooal to be worked into square or rectangular blocks or pillars by narrow places called * stalls,' * rooms,' or * drifts. ' Extracting the pillars and allowing the roof to fall in and fill up the space left. This is usually the most cufficult and important part of the work. The accompanying illustration (fig. 1 10) shows the pillars or stoops, and the stalls, bords, or rooms. Size of Bottom Pillar. — The first important point to be considered is the size of the pillar to be left at the bottom of the shaft to protect the surface buildings and the shaft itself from damage. The size of shaft pillars is given differently by different authorities. A good- sized pillar is one 40 yds. square for a depth of 50 fms., and the size should increase by 5 yds. for every 10 fms. increase in depth of shaft ; i.e. the size of pillar for 60 fms. would be 45 yds. square, and for 70 fms. deep 50 yds. square, etc. Another plaq, which is much adopted in Scotland, is to draw a line enclosing all the surface buildings, such as engine-houses, fans, screens, etc., that it is necessary to protect, and make the shaft pillar of such a size that solid coal will be left in all round this line for a distance equal to one-third of the depth to the seam. The size of bottom pillar may also be calculated from the formula R - V ^ V , where R = radius of pillar in yards, D = depth from surface in yards, T = thickness of seam in feet. Andr^ gives the following sizes as suitable for shaft pillars : — Up to 150 yds. deep, pillar 35 yds. square. tt 175 ,, „ 40 „ „ 200 .. ., 45 II *'*'v If i» ^*' II II the size increasing 5 yds. for every 25 yds. increase in depth. The writer's own experience leads him to believe that safety is secured by making the shaft pillar area equal in length in yards to the depth of the shaft in fathoms. For a depth of 100 fms. the shaft pillar should be 100 yds. square ; for 120 fms. 120 yds. square, etc. The size of pillar, however, must depend on the nature of the coal, the roof and the floor, as well as the inclination of the seam and the extent and nature of the surface buildings. It must also be remem- bered that bottom pillars should have an excess rather than a 10 PRACTICAL COAL-MININO. deficiency of coal, as they are freqiieotly cut up later for new haulage nwds, etc. In steeply-inclined workings at least f of the pillar MODES OF WORKING. 147 sbould be left on the rise side of the shaft, as the ' weight ' always tends downhill. The size of pillars in the ordinary working varies very much in different localities and in different seams. In the Hamilton district of Lanarkshire, in the Kll coal, which averages about 6 ft. thick and is at a depth of 100 fnis. from the surface, a common size is 30 yds. X 20 yds., while for the Splint coal in the same district, which b usually about 6 ft. thick and lies about 20 fms. or so deeper than Ell, the pillar is often 30 yds. x 30 yds. or 40 yds. x 30 yds. The pillars left in the first working are much larger now than was formerly the case ; often in the first working only 8 to 10 per cent, being taken out, and 90 to 92 per cent left in the pillars, according to circumstances. At Milnwood Colliery, Bellahill, in the Splint coal, only 8} per cent, was taken out and 9J per cent, left in the pillars. For determining the sise of pillars the following nile may be used : Allow G sq. yds. of pillar per fathom depth for a 4-reet scam, 8 sq. yds. per fathom for a 5-ft seam, and 10 sq. yds per fatliom for a 6 ft. seam, etc. ; multiply this allowance by the number of fathoms in depth, and extract the sqiiaro root of tlic result. In the case of a 4-ft. seam at a depth of 130 fms., we have 120x6-720; ^720= 26-8 yds. square. The size of pillar may also be ascertained approximately by the formula, S-= - /.^ + 22, where S = 8izo of pillar in yards, D- depth of seam in yards. Taking all things into consideration, pillars as large as possible should be left in during the firut working. If roof and floor are both soft and only small pillars are left, ' creep ' will occur* (fig. Ill), andalargeamoimt of the coal may be entirely lost. * Robbing ' the pillars in an irregular manner may also bring on ' creep,' and large areas of valuable coal have been lost in this way. Pillars sufficient to prevent creep in the firet working may be quite incapable of ft doing so when the work of extracting has commenced. ^,„ m.-showmgci^puiid cnwh. Again, it the roof is bad, the floor hard, and small pillars only have been left, then when a crush comes on the roof will 'spill' or 'ride' over the pillars, neceesiUting a lai^-e amount of 'redding' when stooping is going on, and much of the coal will be crushed into small, of much less value. 148 PRACTICAL COAL-MINING. If both roof and pavement are hard and small pillars are left, the coal will be much crushed, and a large percentage of dross will be got. When this takes place it is called * thrust ' or crush. Another point to be taken into consideration in fixing the size of the pillars is the amount of output required daily. Generally speak- ing, small square pillars are most favourable for a large output, as the stalls are numerous, and help to win out new places speedily. Diref-ifon of Pillars, — Pillars should, as a general rule, be worked lengthwise to the rise of the seam, unless the latter becomes very steep, when it is found more economical to make the long side of the pillars at right angles to the inclination, and so have a larger amount of coal to work from on the level course (fig. 112). The most important point is to have the pillars running parallel with the main cleat, as this secures the best coal at the least cost. Width of Stalls or Kooms,— This will depend almost entirely on Fio. 112. — Direction of pillars. the nature of the roof, but if the latter is good, the stalls should be driven as wide as possible, consistent with the safety of the men. Wide stalls give a much larger percentage extraction of round coal than narrow ones, which is a very important point, except where the coal is to be coked, in which case it does not so much matter about small coal being produced. With a stall 6 ft. wide there will be an average of 25 per cent, dross (slack) ; with a stall in the same seam 15 ft. wide, the average would be only al)out 15 per cent. In Scotland, the * rooms ' and * ends ' are usually the same width, varying from 9 to 1 2 ft. ; in the splint coal of Lanarkshire, which has a rather soft roof, the stalls are usually 8 or 9 ft. wide, but in other seams where stoop and room is pnictised 1 2 ft. is a common width. In the North of England the * bords ' or stalls are narrow, being only 8 to 12 ft., wliile the * throughers,^ or places at right angles to the * bonis,' are often as many yards wide. Again, in other districts, it is the practice to open out both * boi-ds ' and * throughers ' narrow (6 to 9 ft. wide for a short distance), and then to increase the width to 8 MODES OP WORKING. 149 or 9 yds., such methodB being common in Cumberland, for instance. No hard and fast rule can be laid down for the width of openings, the main requirement being to keep the stalls of such a width that the minimum of dross or slack will be obteined with the maximum of safety. Extracting the Fillare. — This is the most important and dangerous part of the work in pillar and stall working, and great care should be exercised in carrying it out. The chief point to aim at is to get out the coal as quickly as possible, without endangering the men or losing a whole 'lift' ('judd ') of timber for the sake of a tub or two of coal. On the other hand, no coal ought to be left in that can Fto. 113.— Eitrkcting pillar*. possibly be extracted. To satisfy both conditions, the pillars ought to bo worked out in a regular maniier, beginning next the goaf or boundary, and working forward in regular order (tig. 113). Too many pillars should not bo removed at once, Aa soon as a section of solid coal has been driven through, it ought to be extracted as quickly as pOBsible, otherwise much loss will take place, and the percentage of round coal will decrease, as pillars deteriorate when left standing long. With the greatest care possible, there is always some loss, varying from 7 per cent, to 12 per cent., in removing the pillars, and sometimes considerably more \n lost through careless working and not setting in sufficient props. The pillars themselves are extracted by taking slices, lifts, or judds ofT them, varying from 12 to 20 ft. in width, — 15 ft being a very 150 PRACTICAL COAL-MININQ. In this way they are reduced in eizc till a small pillar abaut 8 ft fiqiiare is left, this small pillar being then extracted as rapidly as possible. Fig. 114 shows one of the methods of reducing the pillars by taking a ' lift ' oflf each side siaiiiltancously. -tM ' a B n • a A allowing method of e> IS.— ExtnctiDg pillon If the pillars left arc large and square, they are often split into two by driving a road throiiyh their centre, and then estractuig the remainder by taking 'lifts' right and left as siiown in fig. 115. In this way the length of lift b shortened, which in the removal of pillars is a coiiaiderahle advantage. Fig. 1 1 6 shows other methods of extracting the pillars which arc sonietiniefl adopted. -IL ir I ir -IL. ir Fio, 116.— EiCMctingpilUr: In Bome districts, instead of the pillara lieing taken out in lifts, the whole pillar is extracted in one operation, and the waste left packed with rubbish as in ordinary longwall working. It is not, however, always convenient or even xafc to attempt this method. When the roof is bad, and hrc-damp is given off freely, eitraeting the pillars becomes a still more dangerous operation. To be success- MODES OF WORKING. 151 ful in this part of the work, the following rules ought to be carefully attended to : — No naked liffhts ought to be used in withdrawing timber, whether gas has been found or not, and tbe timber should be withdrawn when only a few men are in the pit The lifts should be made as short as possible and not too wide. They should proceed regularly and as speedily as possible. Two ' lifts ' should not meet each other ; one should be finbhed and the timber withdrawn before the other comes forward. The timber ought to be withdrawn as soon as practical after a 'lift' is completed. If plenty of timber be used (about one prop per square foot) less will be lost, and a plentiful supply of timber should be kept as near as possible to the working faces. Panel System. — In the old method of working, the whole royalty to be worked was first cut into pillars right to the boundary line before any of the pillars were extracted ; this entailed a large amount of loss, due to the length of time the stoops or pillars stood before being taken out, for where the roof was bad or the coal tender, they would be much crushed. To overcome this difficulty, workings are now often laid out in sections or panels, and as soon as one section is turned into pillars, these are at once extracted without being allowed to stand any length of time. This method is found both cheaper and to result in the production of better coal. At Hamilton Palace Colliery this system of working was adopted, the whole field being first divided into large blocks or panels, 336 x 356 yds., by pairs of headings or levels driven close to each other (fig. 117) and * throughers ' driven for ventilation. The levels and headings were driven by Stanley coal-heading machines, two machines working a level each with only a rib of coal 1 ft. thick left between them (fig. 118). This rib of coal obviated the use of brattice, and served to preserve the roof ; the rib was subsequently taken out and the two drivages converted into one level 1 1 ft. wide, which was quite sufficient for a double road being laid down for haulage purposes. As the large blocks are formed, men are immediately set to work to form smaller pillars, 30 yds. by 20 yds., and as soon as these are driven a third set of men proceed to extract them. The great advantage of this method of working, as compared with that of forming pillars over large areas, is that they only stand for a short time after being formed, better coal being got^ while a larger number of men 'can be employed, and hence a larger output is obtained. At Clifton Hall Colliery, in the Manchester district, the Doe coal seam is worked on a similar principle. Pairs of levels are driven to the boundary, with 40 yds. between the openings, and 200 yds. above these another pair of levels is driven parallel. When the boundary is reached, a pair of headings is set away to connect them, thus dividing the coal into large blocks 200 yds. square. These blocks are then sub-divided into pillars 30 yds. square, and when a PHACTICAL COAL-MINING. block baa been turned into pillars tbe latter are at once extracted, beginning at the boundary and working backwards. Lifts of 12 yds. lUL =Joanaai H □ a coa atffi aci •» n 1=1 a C3CD an na e_ . _ , UnaooDDiziaoaLJ □□□□□□□□□ani— 1 □adcziaaaaaaLJI ■:, n n i n ii__, AA = ttTic» pilUr Pio. 117.— Panel ajatem. irpBDslB. SB=SnM pilUra. CC=PilUn being eitiactrd. wide are taken off the pillars, a packing 9 ft. wide being carried up alongside tbe road — the material for which is inferior coal. The seam is alt<^ether 9 ft. thick, but the top 3J ft. is left on for a roof ; the holing is done in the 7 in. of fireclay, which is holed for 3 ft. The top coal is then taken down and another 3 ft. holed, until 9 ft. of the bottom coal is bared ^this part of bottom coal being obtained by blastiug. The lifts off the pillara Special Uethods of Working. — When two or more seams are close together, with little strata between them, it ia often difficult to determine the metliod of working best adapted for getting all the coitl out ill good condition, particularly when the strata between the MODES OF WORKING. 153 coal seaiuB are soft and friable, and when the Beams themselves arc largely intermixed with bands of dirt. When two seatoB are separated b; 6 or 10 fms. of strata, it is, ax a general rule, best to work the lower seam out first, particularly if much water is given off, and to let the upper one stand for two or three years. By that time the roof will have settled down gradually and evenly. This plan may coat more than if the upper seam were worked first, but far better results are obtaiued as a rule. Of course, there are exceptions ; for instance, if the top seam had a bad roof, it might be better to work it first, or there may be a stipulation in the lease that the upper seam be first exhausted. When two seams are separated from one another by only a small thickness of rock, and if this stratum be hard and firm, it is better to work the top seam first, allow the roof to settle down, and then work the lower seam. If the intervening stratum lie loose and friable, the bottom scam Coal sT Garni I'll' Fio. IIB.— Section of Beam. should be worked first, as otherwise it may be found impossible to work it at all. Then, ^:ain, sometimes a number of scams occur together, separated only by thin bands of dirt or inferior coal. In a seam having a section, such as in fig. 119, the bottom portion is worked firat up to the bottom of the Splint coal, leaving this on for a roof, white the stone and holings pack the waste, the working being carried on in the regular longwall way until the boundary is reached. Then the top part (Splint coal) is either wrought back from the boundary to the shaft or worked inwards in the usual way, the old roads serving for this working. The main object to be kept in view in working two seams close togetlier is to get as much of both as possible, and not to damage either by working the other. In Lanarkshire, the Splint and Virgin and the Kiltongue seams are often divided by bands of dirt varying from 1 ft. to 6 ft. ui thickness, which renders them dillicult to work, especially when the dirt between the two portions is 4 ft. to G ft. thick. In the Blantyre district, the Splint and Virgin seams are separated 154 PRACTICAL COAL-MINING. by a band of dirt only 1 ft. to 3 ft. thick, and in some of the collieries these seams are worked in two portions. The Virgin seam is worked in the ordinary longwall method, the walls being 14 or 16 yds. long. This coal consists of the Virgin seam and the ply of stone up to the bottom of the Splint coal ; but to give sufl&cient height in the roads a portion of the latter is also ripped down. The walls are packed with the intervening stone, and with any stone resulting from falls of roof on the roads. The Virgin seam is worked in for a consider- able distance in this manner, and then the Splint coal is ower Portion ^"4 Fig. 120.— Section of Kiltongae seam. worked back, what was the packing for the lower portion being now the holing for the top part. The one set of roads serves for both seams. By this method of working, round coal is economically got, but the main roads are extremely difiicult to keep in repair, owing to the insufficient packing of the walls and the weight from the roof. Fig. 120 represents a section of the KU tongue seam as it is found in the Coatbridge district. A common method of working it is as follows : — The bottom portion is worked from 9 to 12 ft. in advance of the upper portion, and short props p p are put up along the wall to support the intervening strata (fig. 121). When the coal has been taken out in the lower seam, the short props are then drawn, and Fio. 121. — Method of working Kil tongue aeam. the fakes allowed to fall, a pack being put in along the face until all the loose material is used up. The top portion is then either blasted or wedged down in the usual way, care being taken to properly support the roof immediately the top coal is removed. This method works very well when the thickness of the strata between the two seams docs not exceed 3 ft. ; when it is greater it is dangerous to work by this system, owing to the difficulty of getting out the short props, and the danger arising from large slabs of the fakes breaking off' and falling over at the face. Any open spaces along the face should be supported by wood pillars. Another method of working this is to keep both portions going as separate workings, and when the road is ripped to put in a short pack in both seams at the same time. MODES OP WOBKINO. 155 When the dirt separating the two scamB is 5 or 6 ft. thick, the following metliod of working is often adopted : — Tlie bottom seam is worked first bj ordinary longwall. Main levels and headings are set away every 40 or 50 fms., and the drawing roads cut otF on one side, and new branch roads are opened on the opposite side of the heading. As the branches are thus cut off in a section, the upper seam is opened up in the old road-heads and the seam worked back towards the main levels (tig. 122), beginning at the level itself, which would require to be worked during the night shift. By cutting up on the ' low ' side of the hrst branch road and the ' rise ' side of the level, means are afforded for an air-current to circulate. In working by this method, the walls and roadways in the lower seam should be built very carefully, otherwise great .-..=Ss, ,,^J. ■^, = «-- ----■^ ir''" ri.- ii-^ ---_-. H sor"~ ■-^; «=^.- Fio. 12-2. —Working apeci&I seams. difficulty is sometimes experienced in reaching the top part of the seam. The advantages claimed for this method are ; It ia safe to work Little tlppiog it required, and keejiiag roodi open is dlBjionsed with. Len expense ia incurred for timber. A larger output is got bj working both seuma practically at the aame time. Sometimes three seams are found within a few feet of each other, as in some parts of the Ayrshire coal-Keld. This greatly increases the difficulty of working. The section here given (fig. 124) repre- sents one that occurs at Dalmellington.* The method of working adopted is very similar to that just described for two seams occurring close together. ■ IbUL, Tol. riv. pj). 113-11*. 156 PBACTICAI, COAL-MINmC. Ill this working two leveU arc driven— the low or main level in the top coal and the higli level in the bottom coal. Sometimes, when the roof of the top portion is not very good, the main levels are driven in the bottom coal. Level croHs-cuts are driven at convenient distances — usnally 40 to 50 fma. — apart, from the top coal in the low level to the bottom coal in the high level. In this coal longwall working are opened out, a barrier being left between the two levels, and branch roads 12 jda. apart are set oflf to the rise at right angles to the level (fig, 123). In the roada of FiOB. 123, 12*. -System of working adopted at Dalmcllington in AyrsMre. this working the diirk fakes are ripped down to the bottom of the mid coal, the roads heiiig pikcked 12 ft. wide. When the brunch roads are worked up 40 or 50 fma. they are cut off by a new level ; only tho.-!0 in a line with the cross-cuts are kept open aa main roads, l>ein|j; afterwards fitted up as self-acting inclines to convey the coal to the low level. When a certain arei* has been exhausted in the bottom coal, a new set of operations is hcgnii at the cnusio * level, by piercing up into the mid uoal and opening out longwall workings in that seam, the roads of the lower scam being used. A pillar is left to protect the cross level, should tins atill be in use when it is reached. The roada ' Seir-ucting inctisi!. MODES OP WORKING. 157 are finally ripped up to the bottom of the top coal, and a pack put in on the top of the dark fakes, which was the roof of the bottom coal, but is now the floor of the mid coal. When the mid coal has reached its limit, the top coal is pierced up along the faces and worked backwards longwall, there being no ripping in this working. Stones from the road-sides and old timber are used for pillars on either side of the road-head (gateway), the walls being propped in the usual way. By this method very little coal is lost, and the percentage of round coal got is larger than when the seams were worked by stoop and room. SpontuieouB Combustion. — In many districts spontaneous com- bustion occurs when the coal is being worked. In the South Staffordshire thick coal underground fires are of frequent occurrence, and in the Dysart thick seam in Fifeshire the coal very readily takes fire on being worked. These undergroimd fires are more or less due to the presence of quantities of dross or inferior coal in the waste. The theory, or rather theories — for there are many — of spontaneous combustion in imderground workings need not be discussed here, and only the methods for dealing with such occur- rences will be dealt with. To overcome the danger arising from underground fires, various means have been adopted. Where the seam is worked on the longwall principle, continuous walls of clay have been employed to prevent the air from entering the waste ; banks of sand have also been used for the same purpose, but neither method seems to be very practicable. When a * crush * came on, a clay wall would, in all probability, be pushed out into the roadway, while such walls would certainly entail a large amount of extra labour and expense in construction. Where these imderground fires are of frequent occurrence, it would seem best to work the seam on the * retreating ' system, i.e, driving the principal roads out to the boundary, and keeping them dipping from the shaft if possible ; the coal could then be worked uphill towards the shaft, and the waste allowed to fill with water up to within a convenient distance from the face. To overcome the danger from underground fires in Fifeshire, the coal is sometimes worked on the panel system. The coal is thick, and is generally worked in two portions (figs. 125, 126, 127). Dur- ing the first working extraction extends to the * cherry' coal, the levels being driven 8 ft. wide, and pillars 30 yds. square left on the *rise' side. The cross Hhroughers' are also driven 8 ft. wide to allow double roads to be laid, as the latter are worked as self-acting inclines. The panels are generally formed 140 to 160 yds. square; and in forming the panel a main heading is driven 8 ft. wide, and pillars formed on each side 30 yds. square. The heading is driven up 80 yds., thus forming two pillars and part of a third one. The regular working is now begun. The stalls are driven 15 ft. wide, and small coal pillars, 6 to 8 ft. square, left to support the roof. 168 PRACTICAL COAL-MINING, No droHB ia filled in this working. Wood pillatB are put in, generally three in each place, this being sufficient to allow the roof to subside gradually. This method is continued until the 30-yd. level above ia reached ; it is then cut off and the coal brought out on the upper road. While working thus, the abandoned workings left behind will subside from 5 ft. at the com men cement to a height of 2 ft. 6 in. A margin of 10 ft. is left next the upper level for protection, and the timber is taken out and the dross filled, the Viaa. 125, I'Jfl. — llj'sait thick nam working. small 8-ft pillars being now cnished to dust. The coal is then worked back, and every place of ingress built up, to prevent air travelling through the abandoned workings. When the honndaty has been reached, the large pillars forming the barriers are worked The advantages claimed for this system are that practically all the coal is extracted, and in the event of any fire occurring it can be easily shut off by driving a level higher up and opening out anew. By this method of working, however, a large proportion of the H0DE8 OF WORKING. 169 coal, and particularly of the pillare, is so badly oniahed as to be of relatively little commercial value. The seams at most of the collieries in Fife are now worked on the two-fold isyBtem. Workiiig Highly-indined Seams. — In working seams that are ' Cart oa' stony Cotli'H Splmt 7Ul2 Fio. 127.— Section of Dyurt thick bwid. highly inclined, from 70° to 90* from the horizontal, it is found, as ft general rule, that whether the seams arc moderately thick or very thin, the best system of working is by lougwall or some niodilication of it ; especially is this the case when the seams reach a certain depth, say 120 to 150 fms. from the surface, when the pressure in 06 Stclion of Great Setm :oaHrreH IB nnti Coal 2 i stone BB O'ff (inferior) ffT Coalffrt^ is' Section of SUirhetd Seam KiGH. 123, 12B.-S«ctionBatNiddrie. highly- inclined seams becomes very great, t'ntil they reach such depths, they may, however, be worked perfectly well by ' bord and pillar ' in the ordinary way. At Niddrie Collieries, near Edinburgh, where the seams are inclined at an angle of 65* to 90° from the horizontal, longwall is now the 160 PRACTICAL COAL-MINING. only system that is practised, although formerly the Beams were worked by 'stoop and room.'* Figs. 128, 11^9 give a section of the two seams most lat^ely worked. The coal is won by both inclined and vertical shnfts, and is worked in lifts of from 60 to 80 fms. in depth, divided into panels of about 200 fma. in length. In each panel, and preferably as near to its centre as possible, a ' brake ' incline is formed, by means of which the coal is lowered from any intermediate roads to the bottom level, along which it is conveyed to the winding incline or shaft. When the dip docs not exceed 70*, the method oF working is as II A B F i Fins. 130, 131.— Longwall Byatem at Niddrie follows :— Close levels (A, B, C, D, figs. 130, 131) are driven in both scams from the winding incline at the depth fixed npon as the bottom of the lift, and when a snfficicnt distance h.Ts been reached they are connected by a cross-cot (B D, figs, 130, 131), and longwall operatioits are then commenced. A level about 8 yds. wide {B, E, G, figs. 130, 131) is act away, leaving 6 ft. of stowage under the rails ; the rise side of the place being continuously timbered with pillars 3 ft thick and built alternately draughtboard fashion, the open spaces being filled with dross. 'Spouts' or 'shoots,' 3 to 4 ft. wide, built and causewayed with piei^s of ironstone, are branched * Mr Hugli JolinaUine, TVniu. ilin. Intl. ScU., vol. x. ji. 204. MODES OF WORKING. 161 off straight to the rise 12 to 16 yds. apart from centre to centre. The goaf is stowed with the daugh or fireclay, dross, rough coal, and any ironstone not required for packings. For convenience in working, the walls are so arranged that each has a long * rise ' side and a very short ' dip ' side. The ' cannel ' coal, which is the part for which the seam is principally worked, is dropped down the spouts (I J, fig. 130), at the bottom of which it is filled by a 'drawer.' At intervfds of about 70 yds. travelling roads (L B, fig. 130) are formed to afford convenient access to the working places at different points. These are built similar to the spouts, and are furnished with ladders. While the longwall is progressing, roads (K, L, M, N, ^g. 130) are driven in the Stairhead seam at intervals of 40 yds., and crosa-cut mines (G N, fig, 130) are driven from thence to the Great seam, so as to strike the latter before the longwall headings reach their level. From these mines, intermediate levels (L N, fig. 130) are carried across the working faces as they come up, cut^ ting off the * spouts,' or what would be, in ordinary longwall, branch roads. The rails for these intermediate levels are ' laid upon the stowage, and the rise side of the road is timbered similarly to the levels. The close level, in the Stairhead seam (D H, fig. 131) is carried in advance of the level in the Great seam, and from it cross- cuts (F fl, fig. 131) are driven, connecting the two seams at intervals of 60 to 80 fms., for the purpose of cutting off the out-bye portion of the Great seam level as soon as the ' spouts ' on it have been cut off by the intermediate level above. The same system is followed with the upper levels, the object being to * shorten the life ' of the roads in the* Great seam and to keep the horse or engine haulage as near to the working faces as possible. The method of building the levels and spouts is shown in figs. 132, 133, 134. The stx)wage on the dip side of the levels tends to prevent the roof breaking and bursting out on the roads. The roof is supported by * half-rounds ' (D, fig. 133), 8 in. X 4 in., placed 4 ft. apart and supported at each end by props 5 in. diameter. The walls are either 12 or 16 yds. long; in the first case two men usually work in each, and three men when they are 16 yds. in length. Very few props are used at the face, but the coal is kept closely 'spragged,' the distance between the 'sprags' or 'holing props' being not more than 3 or 4 ft. When the seam lies at an angle of 90° or in a vertical position, a rather different method is adopted. The plan shown in fig. 135 will explain the system. The brake incline and haulage roads are made in the Stairhead seam as before, and close levels are branched off this incline at distances 18 yds. apart, and from each level a cross-cut mine is driven to the Great seam. In the bottom level (A B, fig. 135), 6 ft. of stowage is kept below the rails, and the rise side of road is well timbered. The height of the roads is 5 J ft. clear. The *rise' side of the place is kept 162 PBACTICAL COAL-MINING. trailing ho bh to form an angle of 45° with the road. As soon as this level has been opened up sufficiently to let the rise side reach the level of the cross-cut mine (C), roads from this mine are laid on the top of the stowage, their rise sides being timbered, and the working >. 132.— Method of sujiiwrtiug ' ahooti.' Kio. 133.— Method of Bupporting level, Fio. 1S4.— Face of working. is again citended to the cross-cut above (D), aud bo on to the top of the brake incline. The roof in this working forms one side of the road, and is supported hy half-round crowns, 8 in. x 8 in. x 4 in. and 4 ft. apart. H0DE3 OF WORKIMQ. u 164 PRACTICAL COAL-MINING. the upper end of the crown being built into the timbering and the lower end into the stowa^. The brake inclines are usually 200 fans, apart, and the coal is worked for a distance of 100 (ma. on each Bide. At Kilsyth, Stirlingshire, the scams sometimes lie at an angle varying from 30* to 45', and here both stoop and room and longwall working are practised. A main incline is driven right from the surface to the dip of the seam, and the coal is worked in ' lifts ' or 'benches' of about 100 fms. each. At each of these 'lifts' levels are set away on each side of the main incline (A B, fig, 136). These levels are filled on the dip side to make the rails lie as horizontally aa possible. From these levels, which are iisually 12 to 15 ft. wide. y/. /? 13S.— Highly inclined working at Kiliijrth. roads are set to the rise, and pillars Formed about 22 yds. square, the openings being the same as in the levels. On every third or fourth roadway to the rise, the coal is brouglit down to the main level by ' cuddie braes,' * which work well enough up to inclines oF about 1 in IJ or 1 in 2 ; when they exceed this, the coal slides down the openuiga, and is filled at the levels into the tube, two planks being put across the mouth of the opening to prevent the coal from sliding out into the main levela. As the coal is chiefly used for coking, the percentage of dross is of no consequence, pulverisation being, in any case, necessary. After a lift of 100 fma. has been turned into pillara, these are them- selves extracted, by taking as many ' slices ' as possible across level course, and a few lifts to the full rise. The tubs are drawn up the main incline in sets oF six or seven, each tub holding about 8 cwta. 'Term nwd in Scotland for balance moliacorjigbrow. MODES OF WOBKtNO. 166 of coal, and being filled only level with the aides. A comparatively wide gauge roadway is used, the width between the raik being 3 ft. 2 in. This is found necessary to prevent the tubs from over- balancing in the levels. Main inclines from the surface work very well when the distance is not very great (300 fms. or so), and when the inclination is steep enough to admit of a cage being used, but where the inclination ia between 30* and 45' vertical shafts are to be preferred, as offering better facilities for winding and for dealing with water. At the Shamrock Colliery, Westphalia, where the seams dip at an Fia. 187. — Hsthod of workiog at Shauirock Colliery. angle of 45*, a rather peculiar and complicated method of working is carried out.* The scam worked is from 7 to 8 ft. thick, and consists of a single bed of coal without any bands of dirt, the holing being done neit the floor. The method of working adopted is illustrated in fig. 137. It ia carried out in stipes or panels of 200 yds. from top to bottom, each panel being served by a main or bottom level. The ground between two main levels is divided into great blocks or pillars 330 yds. wide, by headings B B driven to the rise, which serve as self-acting inclined planes for letting the coal down to the bottom level. These large blocks are subdivided horizontally into three parta by two intermediate levels, and into two parts on the ' Lfctura im Mining, subj. 6, Jip, 82-85, by Prof. Wm. Gtllowny. 166 PRACTICAL COAL-MINING. line of dip by the central heading A, which is used for sending rubbish down into the workings. At the point where the central heading A intersects the higher level, a small shaft X, 20 ft. deep, is sunk to serve as storage room for this rubbish, which is \ised for filling up the workings. The bottom of this shaft is connected to the central heading A by a short, level, crossrmeasure drift. All the rubbish which results from the driving of cross-measure drifts, and from the enlargement of road- ways, etc., as well as that brought from the surface, is tipped into this shaft, from which the men who attend to the stowing of the workings derive their supplies, which are subsequently sent down the central incline A into the workings of the three sub-stages. The three sub-stages provide six level-course working places, three at the points L, M, N, and three at the corresponding points 0, P, Q, on the opposite side of the heading A. While the three working places on one side of the central incline are producing coal, the three on the other side are being stowed, and vice vci'scu When the work of stowing the three places on one side lias been completed, the stowers and miners exchange places. Protection pillars having been left on the sides of the centnil incline, these are now taken out and replaced by stowing after the sub-stages have been exhausted. The lower end of the central heading is always stowed up carefully at the commencement, in order that the air which enters by the lower cross- measure drift may be compelled to pass to the right and left of the sub-stage workings. It then finds its way up the coal inclines, along the haulage roads to the working places, along the faces to the central incline, and through the latter into the next higher level. In the accompanying illustration, A A are central inclined planes, in which the rubbish is let down from the higher level ; B B are inclined planes for letting down coal into the lower level ; C C, bottom level of the stage which is being worked, stowed with rubbish ; D D and E E, levels of tlie sub-stages, also stowed up ; and F F, roads along which the coal is hauled from the working places to the inclines. G G are roads along which the stowing is hauled from the central in- cline to the working places. After these have been driven out to the limit of the sub-stage, these roads become hauling roads for coal from the working places next above. J J are protection pillars, and H H doors provided with regulators for distributing the ventilating current to each set of working places. L, M, and N are working places which, after producing coal for a certain time, are eventually stowed up, and 0, P, Q arc places which are in process of being stowed with rubbish, and are afterwards occupied as working places for coal. R S are short cross-measure drifts to a lower seam, 16- in. thick, in which a level is driven under the workhigs of the lowest sul>stage to form a communication with the main cross-measure drift for haulage and ventilation. The cost of working by this method, with complete stowing, is returned at 2,0'7d. per ton got, including the M0DB8 OF WORKING. 167 coet of laoding the coal at the bottom level. It watt found from experience tliat the additional proportion of large coal obtained by thie syBtem of working compensated to a great extent for the additional cost of complete stowing. At the Teala Minea, Alameda County, California, seams of coal are worked which have an inclination of 60°.* In one of these seams they have adopted a system called the Angle Method of Working. This system is illustrated in fig. I3S. In this system the gangway chutes are driven at right angles to the strike of the seam 40 ft. up the pitoh ; a rrosa-cut 6 ft. by 5 ft, is then driven parallel with the gangway. From this cross-cut, chutes are driven at an angle of 36°, at the same distance apart as Gangwty Fio. ISS. — AnKleByBtem of working at Teslit Mlii»<, Culiforni^ the gangway chutes {30 ft.); cross-cuts for ventilation being driven every 40 ft. between the chutes. After a panel of tive or more chutes has been driven for the required distance, work is commenced on the upper outside pillar, the pillars on that line are drawn and the ne»t line of pillars attacked, and this is coiitiiiucd until the panel or block is worked down to tiie cross-cut over the gangway. About every 80 ft. in this level it is found advantageous to pack a row of cogs, parallel with the strike of the seam, as the pillars arc taken out. This serves to prevent the crushing of the pillare, and prevents any accidents from falls of rock. In the regular working places littlo timber is rc(|iured, as the roof is very good. It is claimed for this system of working that the coal undergoes less breakage than in the method where vertical chutes are used, while in the matter of timber a considerable saving can be effected. * Mints and MiuemU, Oct. ISflH. 168 PKACTICAL COAL-MINraO. Id the No. 7 or Summit scam a rather differeDt method has been adopted. Thix seam averages 7 ft. of clear coal without foreign matter of any kind. The roof ia good, being composed of a shelly iilute, while the floor \a a hard, compact sandatone, and it ia ia this that the chutes, airways, iuclines, and other openings necessitated by this method of working and the characteristics peculiar to the seam are driven. The method of working this seam ia shown in fig. 139. Two double chutes are driven up the pitch, or to the full rise, at a distance of 36 ft apart, connected every 40 ft. by croes-cuta, one side of each chute being used for cool and the other aide as a manway When the seams are thin and highly inclined, a method of working termed 'Grading Renversee' or ' inverted steps ' is often adopted in a Fio. 139. — MstlioJ of working the Summit seam at Tesia Uines, Catifornik. Belgium and other European countries. The seam is worked in the longwall method, with the face advancing in the line of strike. The system is much like that adopted at the Niddric Collieries, which has already l>een fully described. The working face advanoea in the direction indicated by the arrow (fig. 140). The miner, standing on a planking beneath him or perched on the props stan- chioned between the roof and floor, operates on the vertical face of the coal in his stall, while solid coal overhangs him. D ia the drawing road leading to the main haulage road, and receives the coal from the stalls through the chimney C C, left in the gob or waste. Each chimney is provided at the bottom with a hopper door, which is opened when a tub is brought under it to be lilled. As far aa possible it is sought to keep the chimneys full of coal, but, even with careful supervision, this is not always atlained. An obvious inconvenience attaching to these chimneys is the liability of the coal to get jammed, while they always present a source of danger to the passage of men MODES O? WOBKINO. 169 over them. The height of a step or stall, which varies in difTerent localities from 2 to 4 j'ds., is determined by local circumstances, chief among these being the nature of roof and pavement, the amount of gas constantly given off from the coal, and the liability to sndden Fid. liO.—aradi}aBtnT»nA, outbursts of gae. Other things equal, the height of each step regulates the rate of daily advance. When the height given to a stage is considerable, one or more intermediate or false levels {A A, fig. Ul), communicating with the rj- ■ ^ — ^ ';-:'iviT' i?;CC;/<, T'S< ■~» m Fio. 166.— Cross-bar. Fias. 166, 167. -Cross-bar and prop. for the Welsh system are : smaller cost than in using ordinary timber, as shorter crowns are employed and greater resistance to side pressure. On the other hand, the increased cost of preparing the wood and setting it must be taken into account. When the roof and floor are both bad, it is very difficult to keep the roads in good condition by ordinary methods of timbering, and to prevent tlie floor from creeping, * sill ' pieces are often used, and the props notched into them as well as into the crown-pieces. These *sill' pieces, however, have their disadvantages where the floor is given to creeping, for when the road requires adjustment, as it fre- quently does under such circumstances, the * sill * pieces give trouble and often occasion the danger they were meant to avert. At the great Comstock Mine, where enormous side and top pressures have to be withstood, a special system of timbering is adopted. Fig. 158 shows the construction of one of the sets employed. Each set consists of six pieces — a sill piece, top piece, and two pieces for each side. These pieces are usually cut square and notched in the manner shown. Between every two sets a close covering of lagging is laid all round, top and sides. While this system appears to be ratlier expensive, and more suited to rich metalliferous mines, cases have come under the writers notice in which it miglit have been used with good effect in coal mines, as ordinary sets made of heavy Fio. 158.— Wood set, as used at Comstock Mine. TIMBEEING ROADWAYS, ETC 181 larch sometimes only lasted about two weeks, owing to the great Bide and top pressures. When the roof is heavy, yet has no bed of hard rock iu it, and the roads hare to be driven comparatively wide, such as in pony roads and at bnwchingH, it is often very difficult to properly support it. In such circumstances, only the best heavy larch should be used, both fur crown-pieces and supports. Figs. 159, 160 show a method of sup- porting such roads. Crown-trees are set, and temporary props put up to the centre. Other crown-trees are placed at right angles to these, or parallel with the road along the ends of the cross-bars, and to those crowns parallel with the rwd the props are set, the whole being firmly fixed with lofting and wedges. Where roads branch off, FiGB. 169, 190, — Sniniortiiig heavy roofs. diagonal nets are sometimes erected to assist the eross-sets. Often when the road is very wide, and two lines of rails are used, it is a practice to set up centre props as well as end ones ; but while this undoubtedly strengthens the crowns, it often Incomes a source of danger, particularly where there is much traffic on the roads. On the Continent, where great attention is paid to timbering, some peculiar methods are adopted for the support of roads. Figs. 161, 182 PBAOnCAL OOAL-HmiNQ. 162 show two of these methode. In the former an ordinary net of timber is first placed in position, short props d d are then placed cloae against the main props, and on the top of these other pieces e e laid longitudinally and parallel with the roadway. From these longitudinal pieces e c, other posts f> ^ are set at an angle so as to meet in the centre of the cnwB-bar, where another bar a is fixed in line with the road. On wide roads this ayatem has the disadvantage of reducing the space considerably. To overcome this difficulty the method shown in fig. 162 is adopted. Here an ordinary set is fixed as before, and the short pieces and the longitudinal pieces r.c placed as already described. In the centre, and immediately against the crown-tree, is placed a shorter crown b, and against the ends of this short piece are two pieces a a placed at right angles or parallel with the roadway. From the longitudinal pieces ccoa the top of the short props, poets are set at FiOB. ISI, 182.— ContineDtal methods of timbering. an angle to meet the pieces a a. By this method increased space is gained in the roadway. In fixing the timber by either of these methods, the ordinary sets are first placed in position, and then all the auxiliary pieces are fastened to the former by thin wire until the set is completed, and when the pressure comes on the wire is of no more nse. None of these methods has been adopted, to any extent, in this countTy, and it is questionable if it would not be cheaper to build side walls and use iron or steel girders under such circumstances. DriviDg through Loose Ground. — When the roof or sides are very loose and have a tendency to 'spill' or run, a special method of timbering must be adopted. The methods of securing such loose ground arc shown in figs. 163 to 165.* An ordinary set is firet placed in position with posts aa and crowns ee, and if the floor is very soft a sill-piece d is added. Pieces of lagging are then inserted above the crown-trees, and driven in with the ends pointed upwards a few degrees off the bori- sontal. These continue to be driven forward aa the work proceeds. Other lagging pieces are driven in behind the posts, and also inclined '"MethodBofTimberiDg," Cal. SlaU ilming Bunau BulUlin, Ko. 2. TIMBKRING ROADWAYS, ETC. 183 oulwan/s at the end 10* to 1S°, the side pressure gradually bringing them to bear closel; against the props. The two systemB shown in figs. 163 to 165 are practically the same in principle, but differ materially in detail. In fig. 163 the lagging is inserted between the two crown-treea, which are separated by wedgfr«haped blocks, one of which is placed at the centre and one at either end. The lagging is then driven forward, as already Fio. ISS. — Timberiiig in looee ground. deacribed. If the grovind ia very heavy, a 'false set' is erected and the ends of the lagging rest upon it. As the excavation progresses the lagging is driven forward, until the further ends find a secure resting-place on the regular sete. The false set is then knocked out and the same operation repeated with the next set. The only difTerenoe between these two methods is that in the one (fig. 163) there are two crosB-bara — one light and one heavy ; while in the other (fig. 166) the lagging is inserted beneath the advancing ends of the set next behind. In both methods the lagging is kept 184 PRACTICAL COAL-MINING. pointed slightly upwards by the insertion of a block of wood 6, which is placed between the portions already fixed and those being driven. When the lagging is driven forward a certain distance, this block is allowed to drop out. To facilitate driving, the lagging is sharpened to a point at the one end. With these methods, even with the greatest care a quantity of the loose ground will run through and leave cavities behind. Cost of Timber, — The cost of timbering varies greatly in different districts and at different collieries, and even in different sections of the same colliery, and may be anything between |d. and 9d. per ton of coal raised. It will vary with the nature of the roof and floor and of the coal, the inclination of the seam and its depth from the surface, and also according to the method of working employed. The following table shows approximately the cost of timbering in a number of collieries in Great Britain. Table showing Cost of Timbbr peb Ton of Coal raised. No. of TliickDess Depth from Nature of Inclination of Method of Coit Colliery of Seam. Feet. Surface. Hoof. Seam. Working. per Ton. Feet. Pence. 1 2^ to3i 1000 Fairly good Comparatively flat • « • Longwall 3 2 2to4 1050 f> >t 2« 3 2to5 1100 Soft roof • • ■ »f 4 4 Utolf 1550 Bad roof 1 : 5, and upwards »t 8* 5 2ito4 100 to 250 Fairly good Flat, to 1 : 16 Longwall and pillar and stall 2) 6 5} 1050 Soft shale 1 :9 Double sUll 8 7 6i 850 )f Flat, to 1 : 14 Longwall 5 8 H 1200 Shale 1 :20 If 2^ 9 7 1700 Good roof Flat Pillar and stall If 10 5^ 1600 »i 1 :16tol : 18 ft 2* 11 6i 600 Bad roof 1 :20 Longwall 3 12 5 1800 Good roof 1 : 12 f f 1 13 5 1200 Fairly good • • • ff •2 14 4 1150 Good roof 1 : 6 »i In the Govern luent collieries of the Saar district of Germany, the cost of timber is estimated to average 6d. per ton of coal raised. Supporting the Main Soadways by Brickwork. — For main roads and pit bottoms, masonry is used to a very large extent, and prob- ably no better method of securing a road has been devised. It is very much more expensive than timber, owing mainly to the extra cost for excavation, but where a roadway has to be used for a considerable number of years, it will in the end be the cheapest method. There are two principal methods of supporting roads with masonry, viz., by building perpendicular side walls to a certain height and then springing an arch for the roof, and by building the TIMBERING ROADWAYS, ETC. 185 □lasonry all round the roof, floor, and Bides, no part of the walling being built porpetidicular, but each part having a certain curvature. This latter method is undoubtedly the better of the two, and masonry so conatructed is very much stronger, but it is also a great deal more expensive, and unless the road has to stand for many years, and a large output is oipected from it, it is questionable if the expense of such a system of arching would be justified. For most ordinary purposes, unless the floor is very bad and given to creep, the common method of supporting roads by two short perpendicular walla and a top arcb will be found quite efficient. The brickwttlling is put in a in. to 18 in. or 24 in. thick, and a space should be left between the walling and the strata, which should afterwards be tilled in with fine ashes or sand, aa this will greatly assist the arching when the pressure comes on it. Iron or Steel Supports. — Within recent years the use of iron and steel supportii for underground workings has greatly extended, and, in certain circumstances, it is to be recommended. It must, however, be remembered that the conditions under which steel or iron girders can be used underground are altogether difToront from the conditions under which the same materials can be used at the surface. In the latter case, all the conditions to be satisfied can be accurately predetermined, the size and resistance of any supporte required being ascertained by cal- cuhtion. Fio. 166.— St«e1 supiiortB. Underground, these conditions can scarcely be ascertained at all, or, at least, only very partially ; the top weight to be supported may be unknown, and further com- plications are introduced when heavy side pressure is encountered. Instead of the load being uuiforju, as on the surface, it is very varied, and the supports are subject to great and suddenly applied pressure. Steel ginlcrs, however, seldom break under sudden pressure or weight, but nearly always. give indications of such pressure by deflecting in the centre. Girders have been known to show 6 to 7 in. of deflection under great top pressure before breaking. In a large number of mines there are main haulage roads and horse roads where the strata have settled, and where the pressures are fairly uniform. In sucli roads, steel or iron supports can be used with advantage. Again, in return air-ways where the air is hot and foul, and contains a good deal of moisture, wood very rapidly decays and requires frequent renewal, and, in sudi cireumstajices, steel or iron supporta may beneficially replace it. Inm or Stecu FropB. —While iron or steel is better suited for 186 PRACTICAL COAL-MINraO. use as oroBs-bars or crowns, props made of these materials have also been used at the face of longwall workings. They are, of course, much more expensive than tiniber props, and it is therefore necessary that they should be used onlj where they cau be withdrawn and re«et, otherwise the coat would be too great. Cast-iron props are not of much use, as they are heavy and easily broken. Steel girders, of |-J-sectioD, present a somewhat sharp and uneven surface to the roof or to the timber lids when used. To overcome this difficulty Firth's patent prop is used. A piece is cut out of the web at each end, and the top and bottom flanges turned over, which enables the ends to present a flat surface to the roof and floor. A hole a a is punched t'^ra in the web, about a foot from each eJSM end, for the insertion of a book to Fios. 187, 188.— Solvit prop! assist in withdrawing the prop (see flga. 167, 168). Steel or Iron Sets. — These are used in some collieries in Great Britain, but they have a more extended use on the Continent, where, as already stated, more heed is paid to supports for roadways. Steel or iron sets arc best adapted for main rcuda, particularly for roads where the strata have settled. In France and Uermany, a simple arrangement, shown in fig. 169, is used. Iron or steel bars, neighing 24 to 30 lbs. per yard, and shaped like girders, are bent in the form of a horseshoe to suit the roadway and set up 2 to 3 ft. apart. The space between the webs is filled up with planking, IJ in. to 2 in. thick, forming a neat strong lining to the road. This method is said to cost about £2 per yard for a road 7 ft. high and 6J ft. wide at the bottom. Another method, employed in the North of France, is to form the girder in two pieces, curved at the top and joined in the centre by two fish-plates fastened by four bolts. This method is beet suited for heavy roofs and hard sides. Fig. ITO shows the detail of the fish-plates at the centre where fastened. The cost in this cose is estimated at £5, Is. 5d. per lineal yard for a rood 8 ft. wide and 6J fL high. In the Uovemment Lead Mines, in the HartE Mountains, the roadways are supported with flat-bottomed rails, HJ lbs. per yard section. The ends of the iron arch ore lodged in holes drilled in lai^e stones (see fig. 171) set iu the floor and fastened by wooden wedges or cement. Between these stones other stone blocks are TTMBBRING ROADWAYS, ETC. 187 inserted, in order to keep them apart and thus ensure stability. The lining or lofting is carried out with the same kind of rails, each 19 ft. 8 in. long, arranged longitudinally, the flat bottoms being in contact with the base of the flat rails. The cost of supporting roadways in this manner is about £1, 13s. 2d. per yard. Supporting the same roads with masonry costs £2, 9s. Od. per yard, and with timber XI, 2s. per yard (first cost only).* When roof and floor are both soft, and the floor given to creeping, Fig. 169. — Iron sets for supporting roof. the support is sometimes made in two or three pieces curved to suit the roadway and fastened at the joints by fish-plates and bolts as before (see fig. 172). A cast-iron sleeve is often used instead of the fish-plates. The sleeve is made to slip over the end of the girder, and when the pieces are fitted together it is drawn over the joint and fastened with wood keys or wedges. Fig. 173 shows the construction of such a sleeve. At the Altenwald Coal Mines,! near Saarbriicken, iron supports * Trans. N, Eng, Min* UTid Mech, £., vol. xzzvii. p. 137. t Ibid,, p. 138. 188 PRACTICAL COAL-»nNING. are used in the form of an elliptic arch. To prevent the supports from shifting, horizontal props are inserted from arch to arch at the highest points. The plank covering is of oak, and each plank over- laps the other, to allow some play under heavy pressure. The cost for this kind of support was X2, 18s. 2d. per yard. Brickwork would not have been applicable in this case, owing to the continuous settling of the floor. At the Nunnery Colliery, Sheffield,* the main roads were supported by steel girders, which were themselves supported on props of larch wood (see fig. 174). The girders were | -section, 4 in. wide, 5 in. Fio. 170.— Details of fish-plate. Fio. 171. deep, with a web | in. thick, and this was calculated to give the same support as a Norway larch beam 12 inches square. The giixiers were supported on props of larch, 8 in. to 10 in. diameter, and the sets were put in about 3 ft. apart, with lagging above. To prevent the girders from being pushed out at the top by side pressure, a lug or band of iron, 1^ x J in., was shrunk on at each end immediately in front of the prop. In some collieries in Staffordshire, hollow cast-iron props are used. These props have a flange 8 in. diameter at top and 9 in. diameter at bottom (see fig. 176). A chair made for the purpose drops into the top of the iron column and receives a reversed iron rail weighing 50 lbs. per yard. These sets are placed 3 ft. apart and are lofted on top * Ore and Stone Mining, Sir C. Le Neve Foster, Sixth Edition, p. 273. TIMBERlNa ROADWAYS, ETC. 189 with planks or rails, the spaces between these being tightljr packed with stoDea. This method of support mnkes a capital roadway, but is best suited for roads where no great side pressures exist. The cost of this system is £2, is. per lineal yard in an averagesized roadway (see figs. 175, 176). At St Helen's t'olliery, Cumberland,* flat-bottomed steel rails were used to support a main haulage road at a depth of 170 fras. Posts of the same material were likewise employed to support the cross-pieces; figs. 177, 178 show how the rails were secured. The crowns were 10 ft. long and the 8iip|)orling props 6 ft. The latter were set 6 in. off the ]>erp«.'ndiciilar, and were cut and dressed so that * Traiu. .Win. fmil. Scot., vol, liv. pp. 242-240. 190 PRACTICAL COAL-MINING. the crown would rest evenly on the top. The lower end of the props rested in a cast-iron sole (fig. 179), arranged to give a solid foundation. Near the top of each prop, and also near the ends of each crown, were drilled two holes J in. diameter. An angle iron b (fig. 177) was then riveted on the end of the crown so as to fit the upright to which it was bolted, and in this way the legs were fixed and prevented from being pushed out. The sets were placed 2 to 3 ft. between FioR. 176, 1 76. —Cast-iron props. centres and lagged on the top with 3 in. planking, and also, when they could be had, with old rails. A piece of wood A A was fitted in between the uprights to further strengthen them. The rails used weighed 79 lbs. per yard, and cost 38. 6d. per cwt. delivered ; the cost for steel H-girders, weighing 54 lbs. per yard, would have been 5s. 9d. per cwt. The cost per lineal yard for this method of supporting the Figs. 177, 178. roadway, including rails, labour, etc., was £1, 14s. 7d., while the cost of brick arching, 14 in. thick for the same road, was estimated to be £2, 5s. 2d. per lineal yard, showing a difference of 10s. 7d. per yard in favour of the rails. Securing Roads with Brick Walls and Girders. — Main haulage roads and shaft bottoms are often secured by })uilding up a brick wall, 14 in. to 24 in. thick, on each side of the road, and stretching steel H-girders across them (figs. 180, 181). Along the top of the TIMBBKINO ROADWAYS, ETC. 191 wall is laid wcxxl planking, 4 in. x 12 in., on which t)ie girders rest. The wood helps to relieve any sudden pressure to whicli they may be subjected. The girders should be wedged tight, and a runner or strap of iron liied between every two sets to prevent theta from canting. On the top is placed a lagging of square or round timber laid close together, any spaces between being carefully packed. At Milnwood Colliery, Bellshill, the wood lagging was replaced by strips n about 3 in. broad and S or j in. thick. This system is pre- Fio. 1711. — DettiUof wle-|>iece. ferable to using wood lagging, as the latter decays and requires frequent renewal. Sometimes sheeta of iron, about ^ in. thick, are stretched on the top of the girders, and wood lagging put above that ; the sheet iron preventing the wood lagging from dropping on the road when it breaks or decays. In another method of securing roadways by brick walls and girders. Fios. 180, 181.— Brickwork and girders. the latter, instead of being put in straight, are curved from the side of the wall on either side, which is said to increase their strength. It also gives increased height, but, of course, it is more expensive, as more rock requires to be excavated in the roof. The ends of the gilders are laid on sheet iron, thus distributing the pressure over a greater area. The cost of this method is £13, 9s. 6d. per yard. The calculated cost for arching the same roadway was £lh, Ss. lid. per yard. At Lanemark Colliery, New Cumnock, some rather ingenious 192 PRACTICAL COAL-MINING. methods are adopted for supporting the roadwHiys. On each aide of the road, aide walla are built from the rubbiah got from the workinga, cement, mixed with sand in the proportion of one to four, being used to bind the rubbiah together. At intervals along the road, brick pillara are huilt up to the same height aa the stone building. Along the top of the aide walla planks are laid, and on the top of these light ateel girders are atretched acroea the road to support the loof. Figs. 183, 183 show thia method. Where the roof is fairly good and does not require any croas- girdera, the roadways are secured as shown in figs. 184, 185. In thia method the stone and cement walling is carried up to within 4 in. of the roof. In the space tliua left, pieces of wood are placed lengthways, being wedged tightly to the roof. Between the stone and cement pillars a pillar of brick is built half-way up, and on the top of this a short prop is fixed between the pillar and the longitudinal planking. Another variation in this system of supporting roadways is shown Fia. 1S2.— CroaB-Boction. Pra. 183.— Iiongitudinsl section. in figa. 186, 187, in which a continuous wall of stone and cement is built up to about three-fourths the height of the road, and on the top of this building short pillars of brick and short props are carried up to support the wood. In both these latter methods no cross supports are used, the roof not requiring them. In other parts of TIMBKRINO ROADWAYS, ETC. 19: the workings the walls are entirely built of rubbish got from the working and cemented. ThiB kind of wall is found to act better in many respects than brick and lime. It often de- flects to a considerable extent before giving way. The ad- van tt^ea claimed for such methods of supporting road- ways are that only a very small number of bricks are required, compared with thoee in which masonry is used throughout, while walla of this description can be built very cheaply, ordinary workmen being able, without difficulty, to erect them. In pillar and stall working they also prevent alabs of coal from breaking off the pillars and falling ( roadways, — an occurrence which often causes much inco in workings, particularly on main haulage roads. Fio. 184. — Crosg-Bsction. FiQ. les.— Longitadinsl aactian. The advautiq^ of using brick wall and girders for supporting the roadways, instead of brick arching alone, may be stated as follows :— L«m spM* requires to b« oM»T»ted tor a, pven mm, the saving in this rwpwt being nearly 2Epsr cent _ Lgbb time is required for erection, and hence less cost is incurred for labour. Where tlie tttatA are soft, girders c«n be placed as the work proceedB, while with brick erchiiig toroporary support* would have to be used, thus increasing the coat . j i. Girder* can be eadly removed from one part of a mine to another and be used over again, whereas brickwork can aeldoin be removed. The coat of iron or steel girders varies, and will depend to a certain extent on the proximity or otherwise of the colliery to iron- PRACTICAL COAL-HININQ. In 1904 the coat of ^rders was about £5, 10s. to £6, lOe. per ton, and for the variouB Bections in use, which are about 50, 66, and 72 Ibe. per yard, about 9d., la., and Ib. Id, per toot respectively.* Comparing the coat of support- ing roadways with girders with the cost of timber for the same purpose, the first coat for girders will be, approximately, twice as eipenaive, but, on the other haud, they will last four to six times longer than the best wood, and will, aa a rule, give a greater margin of safety. Owing to the varying conditions in different mines, it is impossible to fix any definite weight or size of girder as being suitable for Fio.] 187. —Longitadinsl ■section. a given span. Under comparatively equal loadB,t however, the weights, dimensions, and safe loitds for 8-ft. space girders are shown in the following table : — width ol nugo. i 4 1 1 ».,*„, Load for SFertSpui. Fonnili. 24 9 12 • Jf,B.— The price of gii price of iron ftnd steel. t Traiu. I. M. E.. vol. i lera varies from time to time «ccording to the mirket p. 27*. TIMBERING ROADWAYS, ETC. 195 The following weights of girders are often used for different spans : — Girders of 1 6§ lbs. per lineal foot, in spans of 6 to 8 ft. 22 „ „ „ „ 8 to 10 „ 24 „ „ „ „ 10 to 12 „ The above can, however, only be taken as approximate sizes, and it would be best to err, if anything, on the safe side. In a colliery where the span was 16 ft., the girders used weighed 42 lbs. per lineal foot and were none too heavy. Some of the advantages claimed for iron and steel props over timber are — Thev are lighter and handier to work with than heavy wooden beams.' Giraera give increased space for ventilation compared with timber. There is no pollution of the air as is the case with decaying timber. There is no risk of catching fire ; which is so often the cause of underground fires where the timber is in a dry condition. Strength of Timber. — The strength of timber is not always easily determined, and no definite rules can be given as to the size of props or crown-trees to be used underground. The circumstances prevail- ing in each colliery as to roof, floor, and sides, combined with every- day experience in practical working, seem about the safest and best guides to depend upon. Props set in the workings may be said to break in three different ways, viz. : (a) by fracture or * buckling ' alone ; (b) by buckling and crushing combined ; (c) by crushing alone. In the first case, props generally give way when their length is from twenty to thirty times their diameter, in the second when their length is from ten to twenty diameters, and in the third case when the length is under ten diametera. From numerous experiments on the strength of pillars (or props) of timber, the following law has been deduced : — " The strength of pillars of tvnber of equal sectional areas is inversely proportional to the square of the length." Thus, with lengths in the ratio of 2, 4, and 8 ft. the strength will be in the ratio of ( J)2 : (i)^ : (J)2, or J, ^V, and ^V Taking pillars of the same sectional area, one 2 ft. in length has sixteen times the strength of one 8 ft. in length and four times that of one 4 ft in length. This is well known in everyday practice, and the props are usually increased in diameter, according as the height of the working increases. For ordinary large props the crushing strain is about 1^ to 2 tons per square inch, acconling to the age of the wood and the seasoning it has undergone.* If timber be cut when green, and allowed to season or dry gradually, it is found to gain in durability, as was proved by the experiments carried out by Professor Louis, t who records a gain of as much as 49 per cent, in the strength due to seasoning in ordinary pit props. * Trana, L M, E., vol. xv. p. 352. t lUd., p. 864. 196 PRACTICAL COAL-MINING. This fact is fully recognised on the Continent and at many collieries in France and Germany; the props are thoroughly seasoned in specially-constructed drying sheds before they are used underground ; and in some cases they are seasoned artificially by an electric process which is said to give good results. In a number of tests which were recently carried out by the Government colliery officials in the Saar district, * the same results were obtained. The following table shows the effect of seasoning, as ascertained experimentally, on four different kinds of wood : — Wood BhortJy after Felling. Kind of Timber. I Beech, with bark Fir do. Piue do. Oak do. Resistance to Com- preBBion. Lbs. per S |. Inch. 824S 2802 2631 2475 Specific Gravity. 1084 0885 0984 1235 Wood Five Months after Felling. Resistance to Com- pression. Lbs. per Sq. Inch. 3570 3044 2716 2133 Specific Gravity. 1094 0845 0917 1050 Props artificially dried in a Tempera- tare of 140" Fahr. Resistance to Com- pression. Lbs. per Sq. Inch. 3627 3385 2958 2958 Specific Gravity. 0915 0656 0647 0825 It must not be forgotten that the different specimens tested were special pieces, free from blemishes, and having little resemblance to the ordinary pit prop. The following tables t give the crushing and tensile strains of various kinds of w(X)d : — Strength of Timber to Resist Crushing-Strains in Pounds and Tons PER Square Inch. Minimum Kind of Timber. Maximum Dry. Ordinary State. Mean. Pounds. Pounds. Pounds. Tons Ash 9363 8683 9023 4*03 Beech 9363 7733 8548 3-81 Birch (English) 6402 3297 4850 216 Elm 10331 7950 9140 4-08 Fir (spruce) Oak (English) 6819 6499 6659 2*97 10058 6484 8-271 3*69 ,, (Quebec) . 5982 4231 5106 2*28 Pine (pitch) . 6790 6790 6790 3-03 „ (n*d) 7518 5395 6457 2*88 Larch 5568 3201 4385 1-96 * Gluckau/f Berginspektor ('h. Diithing, 1898, vol. xxxiv. p. 797. t Treatise on the Strength of Materials^ by Mr Thomas Box, 1883, p. 91, TIMBERING ROADWAYS, BTC. 197 Showing Stkbnoth of Timber to Resist Tensile Strain in Pounds and Tons per Square Inch. Kind of Timber. Maximum. Minimum. Mean. Pounds. Pounds. Pounds. Tons Ash . . . 17,860 15,784 17,077 7-6 Beech . . . . 11,326 11,388 11,467 6 1 Birch • ■ • • • • 15,000 67 Elm . . . . • •• • • • 13,490 6 0 Fir . . . 13,448 11,000 12,203 6-5 Oak (English) 15,500 13,620 14,560 6-5 Pine(Ku88ia) . 1 • • • • • a 13,300 5-9 „ (Norway) 14,800 12,400 13,350 6-0 Larch •• • • • t 9,632 4-3 Showing Specific Gkavitt and Weight of Matkrials (Water at 62" Fahr. bring equal to Unity). Materia]. Specific Weight of Measurement Gravity. 1 Cubic Foot. of 1 Ton. Pounds. Cubic Feet. 7-788 485-30 4-615 7-087 441*60 5-070 0-777 48-42 46-260 0-588 36*65 61-130 0*483 30-10 74-410 Wrought iron . Cast iron (British) Oak (seasoned) . Elm. Pine (yellow), scasoneil The following rules apply to bars or beams of timber : — 1. The strength of bars or crowns of the same sectional areas is in direct proportion to their width. Thus a bar 12 in. wide is twice as strong as one 6 in. wide if both have the same thickness. 2. The strength of rectangular beams of the same length and width is directly proportional to the square of their depth (W oc ' d^) ; thus if two bars are of equal width, but one is 6 in. deep and the other 3 in. deep, their strength will be in the proportion of 3^ : 6^ or 9 : 36 or 1 : 4, i.e. the prop 6 in. deep will have four times the strength of one 3 in. deep. 3. The strength of bars of equal sectional area varies inversely as their lengths (W oo \). Thus a bar 12 ft. long will only have half the strength of one 6 ft. long, the sectional area being equal in both. FormulaB for Strength of Beams of Timber. — Different formuke are given by different authorities for finding the sizes and breaking weights of beams of timber, all of them giving slightly different results. But it must be remembered that most of the formulse applied in engineering give only approximate results, and are not meant to be absolutely correct, as is the case with the formulae employed in problems in pure mathematics. In engineering, materials for construction are generally allowed a large marginal factor of 198 PRACTICAL COAL-MINING. safety, and there is, therefore, not the same necessity for very fine theoretical calculations. Let L=: length of beam or span in inches B= breadth D= depth W= breaking load in tons K = coefficient of rupture The value of K for different materials has been' found by experi- ment, and is given below : — Wrought iron = 3 '40 Beech = 0 '66 Cast iron = 2 '30 Fir =0*60 Ash = 0-95 Oak = 0-76 Pitch Pine =075 Larch =076 (1) Both ends supported and beam loaded in the centre. W i- 4R -=— . L TKTfl (2) Both ends fixed and load in the centre. W - 6Kqp- . L BD* (3) Both ends supported and load evenly distributed. W» 8K-^|^ • Li (4) Both 9ndB fixed and load evenly distributed. W = 12K-=— • L In circular beams of radius 11, substitute 4*7R^ for BD^ in the above formulae. These rules are very difficult of application to mine timber, as the load is very rarely either at the centre of the beam or evenly distributed along its length, and there is also the side pressure to take into consideration, which, in underground timbering, is often greater than that from the top, and can never be accurately measured. The pressure per square inch due to the weight of the overlying strata alone would be equal to D x '434 x B ; where D = depth or thickness of overlying strata, B = specific gravity of strata, and '434 = a constant number (average specific gravity of strata is about 2*5, taking water as unity or 1). Strength of steel or wroughl-iron girders of ff- section : — When W = breaking load in tons, A = area of one flange (either top or bottom) iu square inches, /= tensile strength of material in tons }ier square inch (generally from 22 to 28 for steel and 18 to 20 for wrought iron), D= depth of girder in inches (including both flanges), L= length of span in inches. Then W-4/^. Li The safe load is generally taken at |th to |th of the breaking load for steel girders. EXAMPLES. (1) Find the breaking weight at centre of a pitch pine beam, 12 in. deep, 8 in. broad, and 18 ft. between the supports, ends fixed and load in centre ; also find TIMBERING ROADWAYS, ETC. 199 the depth of beam required for a breaking load of 24,000 Ibsi, if the width of beam is 6 in. and the distance between the sup[K)rt8 12 ft., load unifbrndy distributed. Suppose the beam to be fixed at both ends, then (a) W=6K^ (6) W=12K^ = 6 X 764^11?^ 2J000^,2x75lii^ 18x12 2240 12x12 _6x76x8xl44 24000_12x 76x6xD' 18 X 12 2240 "" 12 X 12 .-. W=24ton8 .-. 112xlx075xlxD»=2400xlxl. The breaking strain is, therefore, 24 tons. The depth of beam required would be 5*3 in. (2) If abeam 10 in. broad and 14 in. deep has a breaking strain of 30 tons, what length of span would it support under a maximum load, supposing the beam to be simply supported and the load to be in the centre 1 HereW = 4K51^, L .-. 30=4 X 76i?4^'» *^^ 80 L = 4 X 76 x 10 x 196. .-. L=4x 76xl0xl96^^^^g .^ ^^ ^^.g ^^ 30 (3) What would be the breaking load of a wrought-iron girder of H -section, with top flange 4^ in. broad, deptn of girder 6 in., and span between supports 10 ft. I Taking the tensile strength of wrought iron at 20 tons. W = 4/^=.x20i4-;^i;^« = 81ton8. •^ L 10x12 Preservation of Timber. — Timber required for use underground, or, indeed, anywhere, should be felled during the winter when it has but little sap in it, because sap in wood ferments and produces rapid decay. It should also be well seasoned before being used, and if these two points are carefully attended to they are frequently all the timber requires to preserve it. The bark should also be removed before the timber is used underground ; if this is done, there is less liability to decay, and when this does set in it is easier detected. Various methods of preventing dry rot have been tried. Good ventilation is necessary, as timber decays much faster in foul, hot air than in a pure atmosphere. Water is also a good preservative, and in some places the shaft timber is kept wet for this purpose. The water acts by washing off the spores of the fungi as fast as they are formed. 200 PRACTICAL COAL-MINING. The various methods of preserving timber : — By common salt dissolved in water. By impregnation with metallic salts, such as sulphates of copper and iron, chlorides of zinc or magnesium, etc. By the use of creosote. By coating with tar, etc. Timber is often treated with brine made with common salt, in the proportion of 1 lb. of salt to four or five gallons of water, the timber being allowed to get thoroughly soaked with the solution. It has the advantage of being cheap and easily applied. Sulphate of iron is also much used, and has the recommendation of being effective and economical. Chlorides of magnesium and zinc are used for preserving timber. In the zinc process, a solution of chloride of zinc is forced under pressure into the timber. The solution consists of one part of liquid chloride of zinc (specific gravity of 1*5) mixed with 35 gallons of water. One gallon of this solution weighs 15 lbs. and contains about 3^ lbs. of metallic zinc. This process is said to make the wood firm, hard, and proof against the attacks of insects and dry rot. Aitken Process, — In this process the timber is soaked in boiling water containing a strong solution of common salt and chloride of magnesium. The proportion of common salt to the latter should be 7 to 1, and a certain proportion of imdissolved salt requires to be kept at the bottom of the tank used for steeping. The timber treated should be free from bark, well seasoned, and thoroughly dry. The plant used at the Niddrie Collieries, near Edinburgh, where this system is in operation, consists of two rectangular iron tanks made of ^-in. boiler plate, 19 ft. long, 4 ft. wide, and 3 ft. deep, built into a brick seating with a hearth beneath. The boilers are fired with dross, and the tanks have a covering of loose boards. The props are boiled for forty-eight hours ; pitch pine and larch require longer treatment than softer woods. When the timber is removed from the tanks, ic is stacked in a covered shed with free access of air, to dry, as it is quite soft and not fit for immediate use. Cost of rising Preparation, — With the above plant 15 tons of timber can be treated weekly at a cost of £2, 12s. 8d., or about 3s. 6d. per ton, which represents about Is. 5d. per 100 ft. of 6-in. diameter prop wood. The plant itself costs about XI 00. The process is said to make the timber brittle, and when it is used as ' sleepers ' on roadways the nails do not hold well, owing to the oxidation occasioned by the salts present. To overcome this difficulty galvanised nails should be used. This method of treating timber is employed at a number of collieries in Scotland, among which are the Cadzow Collieries, Hamilton ; Auchinraith Colliery, Blantyre ; the Leven and Lochore Collieries, Fife ; and others. Creosote XfetJvods. — Impregnating timber with crude creosote, which was first tried in 1842, is one of the best methods of preserving TIMBERING ROADWAYS, ETC. 201 timber, but such timber has the great disadvantage, particularly for mine work, of being very readily ignited, and is, therefore, less suitable for underground work than for other purposes. For railway sleepers at the suiface, and even miderground, where no danger of fire exists, creoeoting adds greatly to the ' life ' of the wood. The effects of creosote are threefold : (1) it fills the pores and prevents saturation with water ; (2) it destroys organic life ; (3) the carbonic acid coagulates the albuminoids present in the wood and prevents decay. Coed Tar, — Painting the timber with liquid tar is sometimes resorted to, but this also confers the disadvantage of being easily ignited. Painting the props with ordinary whitewash is also a plan adopted, and one which gives fairly good results. While preservatives un- doubtedly prolong the life of timber in underground workings, they seem at the same time to decrease its strength to a considerable extent. Professor Louis has made a number of experiments,'*' which show that timber thoroughly creosoted was diminislied in strength to the extent of 8*5 per cent., while woods treated by the Aitken process were weakened from 8 to 20 per cent., according to the kind of timber treated. The following table t shows the results of tests made at Saint Eloy, on the relative duration of differently preserved woods (uu- preserved wood = 30) in France, upon different methods of treating oak, fir, pine, beech, birch, and poplar woods. Two specimens out of every ten experimented on were used in the natural state. The others were treated with solutions of (1) tar, (2) chloride of zinc, (3) sulphate of copper, (4) sulphate of iron, and (5) creosote, respectively. Name of Name of Wood. Preservative. Oak. Fir. Pine. Beech. Birch. I'oplar Tar, 287 263-5 87-5 105-4 26-2 150-5 Chloride of zinc, . 10-5 60 0 26-3 18-6 52-5 347 Sulphate of copper, 421 12 0 8-0 1-8 2-5 15-6 Sulphate of iron, . 18-0 12-5 4-2 47 37 2-9 Creosote, 17 2-5 4*4 0-6 3*3 1-3 Solutions of molasses have also been used successfully on the Continent and elsewhere. * TranM. Inst, M, E., vol. zv. p. 852. t Coniptes-rendua menmel des Riunions de la SoeiHd de VlndudrU MiniraU, 1890, p. 226. CHAPTER X. WINDING COAL. Preliminary. — The operation of winding or raising the coal from the underground workings to the surface is one of the most im- portant parts of the daily work of a colliery, for, in many cases, the output is limited only by the means available for raising the coal. When once the winding machinery is erected, it is clear that whatever the demands may become, the quantity of coal raised per day cannot exceed the capabilities of the machinery or the winding pow^er. It follows, therefore, that what may be termed increased cost in the winding gear is of very small importance, when compared to the great advantage that may accrue from having, what may appear at the time, superfluous power which can be employed in case of need and if the output is capable of extension. All other surface arrangements must be subsidiary to the necessity of dealing effectively with the coal when drawn, otherwise much vexatious expense and delay will be entailed. Pit-head Frames. — Pit-head frames were at one time almost entirely constructed of wood, but of recent years wrought iron and steel have been extensively used in their construction. Where a frame has to stand for thirty to fifty years, or possibly longer, it is a matter of economy to adopt iron or steel structures, as they are more stable and are not liable to decay like wood frames. For high frames, and for the heavy loads now raised at modem collieries, it is almost imperative to build the frames of steel. In cases where timber is employed pitch pine is generally selected, the size of the wood depending upon the height of the frame and the load to be raised. The following sizes are often used in practice : — for frames 20 to 30 ft. high, front stays and main supports 10 to 12 in. square ; for frames 30 to 40 ft. high, front stays and main supports 12 to 14 in. square ; and for frames 40 to 60 ft. high, the whole of the wood would be 14 in. to 18 in. square. Pit-head frames are usually of two kinds, single and double, both sorts being largely used, according to the preference of those erecting them and the class of work for which they are designed. For heavy 202 WINDING COAL 203 loads and where pumping is required and tackling has to be fixed to thb frame, the double type of frame is most suitable ; a further Flo. 188. — Side elevatioD. Fig. 189.— Front stays. advantage being that pulleys for haulage ropes can easily be erected on them, so saving the erection of another frame for them ,s5''lg Fig. 190.— Back ttUys. Fig. 191. — Side elevation. close to the pit mouth where the room can often be ill spared. Where no pumping is necessary, a good single frame is, on the other 204 PRACTICAL COAL-MINING. hand, just as good for winding, is neater, more easily erected, and is less expensive than a double one. Fig. 192.— Front stays. Fig. 193.— Back stays. Figs. 188-193 show two good types of double wood frames. MmB"^: Figs. 194, 195.— Pit- frames and pit head-gear. Figs. 194, 195 show a type much in use at large collieries in WINDING COAL. 205 1 k'" 4^i Scotland, and known locally as a 'table frame.' Where much pumping is done, and block-and- tackle pulleys have often to be suspended from the frame, or, as is the practice at some collieries for the pulleys for haulage ropes, as well as the winding pulleys, to be placed on the frame ; then this type of table frame is possibly the best form that can be adopted. The whole construction should be firmly and carefully put together by careful and experienced workmen, and the parts fitted together previous to its erection, so that every part fits exactly. The cross-stays should be morticed into the uprights, about 3 in. being generally allowed, all the parts being well boimd to each other by good, strong wrought-iron glands and plates. Fig. 196 shows the details of these glands and the manner of fixing. The wood in the frame should be 8 smoothly planed, and two or three good coats .fm. of paint should be applied to preserve it from the weather. It should also be repainted every second year at least ; this will prevent decay setting in. Generally, the back and front stays are fixed at the bottom on sole-pieces running across the front of the pit and at right angles to the end of the back stays. These sole- pieces should rest on a good foundation of brick or concrete above the surface of the ground, to prevent moist earth from coming in contact with the wood, which will help greatly to prevent decay. Probably the best way is, however, to omit these sole-pieces and to fix the ends of both back and front stays into cast-iron shoes which rest on, and are firmly bolted to, pillars of masonry or concrete. The seam at the top of the shoe should be well filled with putty to prevent water lodging, otherwise this method of fixing is of little advantage so far as the prevention of decay is concerned. The position of the back stays in regard to those in front is a very important consideration, as it is on this part of the frame the tension due to the winding ropes exerts itself. The back stays ought to be put up with a fairly large angle, otherwise the frame is liable to be drawn over by the tension or pull on the ropes ; on the other hand, they ought not to be erected with too large an angle, other- wise their own weight will exert a pressure on the front stays and tend to push the latter out of position. A good plan is to make the distance between the centre of the shaft and the foot of the back stays about equal in length to the height of the frame, or even longer; or else the distance should equal the height of the frame multiplied by the sine of the angle Fio. 196. — Manner uf fixing glands. 206 PRACTICAL COAL-MINING. made by the ropes with the pulley and drum. Suppose the pit- head frame is 60 ft. high, and that the angle that the ropes make between the drum and pulley is 50°, then 60 x sine 50° (0*7660) = 45 '96 ft., the distance the back stay ought to be from the centre of the shaft. The position for the back stays may also be found graphically by employing the principle of the parallelogram of forces. Let a; y be the ground line (fig. 197), d the position of the drum, and p the position of the pit-head pulley. Draw a line a d between these two, and another line ac representing the part of the rope hanging in the shaft to which the l(md is attached. Ascertain what the total load to be raised amounts to. Now, along the lines ad Fio. 197. and ac, two forces which are equal and opposite to each other will be acting, the force along ad being that due to the pull of the engine required to raise the load, while the force along the line ac will be exerted by the load itself pulling in a downward direction. With any suitable scale, say 1 in. to represent 1 ton of loEid, lay off the distance a c eqiial to the total load, and along the line ad lay off the same distance ag] but to allow for con- tingencies, such as undue strain due to an over-wind, wind pressure, etc., it is better to make the distance a h along the line a d equal to twice a e. From the point h draw a line h e parallel to a c, and another line ce parallel to ab; a line joining the points ae represents the resultant of the forces a c and a 6, and the point / where it cuts the ground line will be the position for the back stay. Iron or Steel Frames. — As already stated, pit-head frames are often constructed of iron or steel. On the Continent the frames are WINDING COAL. 207 sometimes made of tubular material, but this type of frame has never come much into use in Britain ; those most generally em- ployed being constructed either on the lattice girder principle or of angle iron in conjunction with box girders. Figs. 198, 199 show a frame mainly made in this way, 70 ft. high, which is less expensive than a lattice girder frame. The cost of such a frame would be about £350, including erection. At Palace Fio. 198. — Steel frame (fude elevation). Fiu. Itf9.- Steel frame (back stays). Colliery and Bent Colliery, Hamilton, the principal parts of the frames are constructed of ordinary railway rails and lattice work on the back stays. Figs. 200-203 show this class of frame, which makes both a neat and strong erection. Winding Engines. — Winding engines may be divided into two classes, viz. : (1) Direct-acting coupled engines; (2) non-direct-acting geared engines, either of which may be horizontal or vertical. The best type of winding machinery is a pair of coupled direct-acting PRACTICAL OOAL-MINING. F(o. 201.-Kmnltt.y8. KiQ. S02.— BkU auys. WINDING COAL. 209 engines placed horizontally, as they are efficient, compact, easily cleaned and repaired, and well in view of the engineman. Figs. 204, 205 show the general arrangement of a pair of horizontal direct- acting engines. Condensing and expansion forms of winding engines have not been much used owing to their difficulty of application for colliery work, the rapid winding and frequent starting and stopping being against their working economically. At a few collieries, however, they have been employed with fairly good results. Coupled engines working at high pressure and provided with Fios. 204, 205. — Horizontal engines, with both cranks shown in position at end of stroke. automatic cut-off valves are possibly the most efficient and economical type of machine for winding coal, as their working parts are few and not so complicated as in compound condensing engines. Single-acting engines may be employed for winding small outputs from shallow shafts, if geared and fitted with a heavy fly-wheel. Such engines are not, however, to be recommended, as they are very unsteady in their motion, and occasion delay and annoyance when they stop on a * dead centre.' The following conditions should be satisfied in a good winding engine : — 14 210 PRACTICAL COAL-MINING. It should be aa direct-acting as possible, t,e. the connecting parts between the piston and the crank shafx should be few in number, as each part entails a waste of power. The moving parts should be strong to resist stresses, and at the same time light enough to offer no undue resistance to motion. Parts moving upon each other should be carefully and smoothly machined in order to reduce friction to a minimum. The steam should reach the cylinder easily at the proper time, and should also be able to leave the cylinder as easily. The engine should be capable of being readily and immediately stopped, started, or reversed. Speed of Engine, — The speed of winding engines varies according to the size and class of engine, but 250 to 400 ft. per minute, as the rate of piston travel, is considered good speed for winding engines. Position of Winding Engine, — The laying down of the winding engine in a proper position is a very important matter. The exact site will, of course, depend on the position of the winding drum, as the engines should be placed at a suitable distance back from the shaft to afford sufficient inclination for the ropes from the pit-head pulleys to the drum. The distance tliat the drum should be from the centre of the shaft ^^^M- Fio. 206. is equal to about 1 to 1^ times the height of the pit-head frame, which will give a fairly good angle for the ropes to work at. Some- times the position of the drum is fixed so as to give the winding ropes an inclination of 45" with the pulleys. Having determined the exact position of the drum in relation to the shaft, it must be set oif with great accuracy, either by measure- ment alone or with the aid of the theodolite. The method of procedure is to get the exact centre of the shaft, or centre of barring on either side of the pit, by means of two cords, a a^ and b b^ (fig. 206), stretched across the pit at right angles to each other. From the centre of these two cords take another cord 0 c, equal in length to the distance the drum has to be placed from the centre of the shaft, and drive a stake at c. If the cord is in a straight line, the point c will be the centre line for the drum, but it should be tested by two side cords, a c and a^ Cy the exact lengths WINDING COAL. of which can be calculated, smce ae^^oe' + oa*, and likewise a^<^ — oii' + a'<^. Both these cords should then be t^en, and if the Plus. 20T, !08, 2W. point c haa been properly fixed, the ends of ae and a'f vrill alao coincide with this point and give the centre line of the drum. 212 PRACTICAL COAL-MINING. Engine Seals. — Winding engines are secured in their poBition by aeatB of wood, brick, or concrete, or a. combination of the two latter. For small single cylinder engines wood seats may be used, as they are easily put into position and are cheap at first cost ; but they have the disadvantage of being easily set on lire and are not so stable as brick or concret*. The wood may be cither pitch pine or oak logs — generaJly the former is used — the principal beams being IS in. to 34 in. square and the Sjwr »g ft " ■ others 12 in. to 16 in. square. For an engine with cylinder 18 in. dia- meter, sixteen or eighteen beams would be required, and, as pitch pine costs Is. 6d. per cubic foot, the cost of the engine seat would be from X20 to £30. Figs 207-209 show the arrangement of a wooden seat. Brick or concrete seats are, however, preferable to those made of wood, as they give the engines a firmer foundation and a more solid bed, and are not susceptible to fire. Figs. 210-212 show tbe construction of such a seat composed of brick and concrete for a pair of horizontal winding engines, with cylinders 25 in. diameter. To fix the binding bolt«, wood rhones 4 in. square are generally built in at the exact position for each bolt, and a set of 'pigeon-holes' left along the foot of the seat to fix the washers and cott«r on the binding bolt. Brickwork for engine seats costs about 158. per cubic yard, including labour, etc. ; cement alone ISs. per cubic yard; and concrete alone, 18s. to 128. 6d. jwr cubic yard. Winding Bopes. — The different forms of winding ropes used are : (I) flat, (2) circular, (3) tapered; and the materials used in their construction are : (o) hemp or other fibres, (6) iron, (e) steel. Hemp ropes may be conveniently used for shallow pita and light loads, because of the facility with whicli they can lie made to coil round small drums. They are also much used on winches for other colliery WINDING COAL. 213 work. The great objection to their use under other conditions is their weight ; the weight of hemp rope for a breaking load of 20 tons would be about 20 lbs. per fathom, while the weight of a steel rope for the same breaking load (20 tons) would only be about 6 lbs. per fathom. On the Continent of Europe ropes made of Manilla and of aloe fibres are greatly in favour, even for very heavy loads and deep pits, and seem to be preferred to steel ropes, and they are said to give good results both as to wear and safety. Iron Hopes are still a good deal used, and are recommended by some as superior to steel, both as regards wear and in affording better indications before breaking, besides being more pliable. But with the different qualities of steel now in use, these advantages over steel ropes no longer hold good, as varieties of the latter can now be had suitable for work under almost any circumstances. There are four qualities of steel wire used for making winding ropes, viz. : — per sq. in. sectional area. Extra plough steel with breaking strain of 110 to 120 tons. Mild ,, ,, ,, 95 to 100 Best patent „ „ ,, 80 to 85 Bessemer „ „ ,, 40 to 45 For shallow pits where the load is light, it is found that Bessemer steel ropes are the most economical, because the first cost is con- siderably lower than that for those made from higher qualities of steel. FlcU Steel Ropes, — This kind of rope is not much used for winding, nor is it to be recommended for such purposes. It is more difhcult to get a perfect flat rope than a circular one ; the latter throughout being made by machinery, whereas the stitching of the flat rope is done by hand. The disadvantages of flat ropes are : — Greater first cost, such ropes being 30 per cent, to 50 per cent, more costly than circular ones. Very much shorter life. Greater liability to failure. Against this, the only advantage is the greater diameter of the drum of the descending rope which assists to lift the load at the beginning of the wind. Circular Ropes, — These ropes are most largely used and are made of from four to seven strands, each strand consisting of five to thirty- seven wires, and for some purposes even more. Haulage ropes are preferably made of six strands, containing seven wires each. The strands are usually laid round a hemp core, made of long fibre Russian hemp, or where cliper are used, as in haulage, of Manilla hemp, which has a harder fibre and is less liable to deteriorate. This hemp core should be carefully treated with linseed oil or other preservative, to prevent wasting from internal friction. Wire of a soft quality steel is preferable for haulage, especially 214 PRACTICAL COAL-MININO. where clips are used, and because it bends round quick curves with case, and winds round small pulleys without injury. The essential features in a good winding rope are flexibility and strength, and it is desirable to obtain these qualities with the least possible weight. The weight of a winding rope is a very important matter ; the dead weight to be lifted by the engine should be as little as possible. Another point to be considered is that the strength of the rope is in some degree dependent on its own weight, as the weight of the portion suspended in the shaft must l)e subtracted from that of the safe load. Life or Durability of Bnpes. — This will in a great measure depend on the treatment they receive and the work performed daily. Mr W. K Hipkins states that the life of a rope will depend on the following points : — The quality and temper of the wire, having regard to the streases the rope has to bear, and the conditions under which it has to work. Its construction as regards number of wires, strands, and nature of core. The ratio of the lay of its wires to that of its strands, and their proportions to the diameter of' the dram or pulley over which it works. The nature of the dressing with which it is lubricated, and the mode and frequency of it« application. The number and angle of the turns it is required to make in working. All ropes ought to be well tested at stated intervals, by taking a piece nearest the cage and applying tensile and torsion tests to each individual wire. The tensile test consists in fracturing the wire by direct stress. The torsion test means that the wire must stand a certain number of twists in a length of 8 in. without cracking. The bending test is sometimes used at collieries, and consists in fixing a single wire in a vice, and then bending it at right angles a given number of times to see whether the wire shows signs of failure. Winding ropes should also be re-capped at least every six months, as this gives an opportunity of examining the inside wires, and also changes the lifting point of the rope on the pit-head pulleys. Ropes should also be well dressed or lubricated, the hibricant to be applied with a stiff brush. Wherever practicable, the rope should be allowed to run through a trough, having brushes filled with the lubricant fixed on either side. Ropes treated with a good lubricant last from 25 per cent, to 50 per cent, longer. The dressing should be applied at least once a week. A good lubricant is made from the following ingredients : tar, summer oil, mica and axle grease, in varying pro- portions to suit varying conditions. The tar and oil must be free from acids. This combination is said to thoroughly penetrate the wires and prevents rust and so fills the cable as to give it an appear- ance of solidity ; it resists water successfully, and does not strip. It is stated to cost only about one-eighth as much as ordinary lubricants, and to give better results. Oare and Management of Bopea. — Wire ropes ought to be care- WINDING COAL. 215 fully stored, and should on no account be placed on the ground, but upon sound planks raised several inches from the soil, so that they may be kept free from damp ; they should also be covered over with tarpaulin and inspected frequently, besides having a coating of some lubricant at regular intervals. Care should be taken in uncoiling wire ropes to prevent ' kinking * ; they should, during the process, be placed on a reel or drum when being ' paid ' out. During working, the greatest stress on a rope being at the moment of starting, every care should be taken to ensure perfect steadiness, as jerking is very bad for ropes. No rope should ever be changed from a larger to a smaller drum, but it will do no harm to change it from a smaller to a larger. If the following precautions are taken and carefully carried out, few accidents will occur to winding ropes : — Choose a f^ood quality of rope from a maker of good repate, and pay a fair price for it. Make minute examinaiionB of the rope at frequent intervals. Protect tiie roue as far as possible from the action of the atmosphere and from water oy frequently lubricating it. Recap the rope and reverse it every six months. Test portions at regular intervals. Discud the rope after it has been in use a certain fixed time, even if it is apparently sound, so far as outside examination shows. A careftd record ought to be kept of all ropes, showing the length of time at work and the quantity of mineral raised by them, and also the speed at which they worked, as it is only by doing so that a fair comparison can be instituted between dififerent ropes. Bope Cappings or Attachments. — The proper capping of winding ropes is of great importance, for it is at such attachments that the rope wears quickest^ and consequently where it will be most likely to give way. The cappings are fixed on the ropes in a variety of ways. In the old method, which is still used to a considerable extent, the capping is formed by two semicircular sockets which nearly surround the rope, thickened out at the bottom end and formed into a link for attaching to the cage chains (fig. 219). The rope is fixed in this cap by rivets which pass through the capping and rope. To secure the rope properly, a part of the end is taken and the wire strands frayed out and bent back on themselves, the part of the rope to which this is done being firmly wound with tarred cord and tapered upward, to suit the shape of the capping or socket. When this is finished the socket is fitted on, and holes are carefully made through the rope with a marlinspike, to coincide with the rivet holes in the capping ; as each hole la made, a rivet is driven through and well hammered when in position. This method gives fairly good results if the riveting is done carefully, but there is always the possibility of damaging the wires when the rivet holes are being made. 216 PRACTICAL COAL-MINING. Another method is to use a socket wit)i hoops, as in figs. 313-215. The rope is treated as already described, and drown into the socket, and the rings then hammered firmly down into position. A third method is to use a solid conical socket or capping, which requires neither rings .nor riveta (see fig. 216). The capping is made witli a conical opening, and through this opening, and for some foct beyond, the end of the rope is drawn. The strands are now opened up as before, and laid back over themselves, some of the wires being cut off, and the rest carefully wound with copper wire until the end of the rope iteelf assumes a conical form ; it is now drawn into the socket and is ready for use. Except under very exceptional circumstances, it will be impossible to dt&w the thick end = socket or oapjiiDf;. = hollow conical plug. = wirG lapping on rope. = wire binding. =looee rings. Fioa. 313-216. Fio. i\t. of the rope througli the small end of the socket unless the capping were to split, which rarely happens. For additional security where heavy loads require to be raised, a collar isshnnik on. Figs. 218, 219 show the meliiod of attaching flat and circular ropes respectively with capels and clamps. Strength of Sopet. — The strength of ropes naturally varies accord- ing to the quality of the material of which they are constnicted. In winding-ropes a large mai^in of strength should be allowed, and the gross load, including the weight of the rope between the pit-head pulley and the cage at the commencement of the lift, should never — except in rare cases — exceed one-tenth of the breaking strain. The following formulte are often used for finding the size of ropee WINDING COAL. 217 for a given load, or to calculate the breaking load for a given size of rope, Tbeue formultc give only approximate results, and are not Strictly correct in every case. (OThonW^Cx SS.-. C=\/^ or 0:=v/-_^ for bamp ropes. (2) W = 0'K 1-60. ■.C=\/^orC=^*^;i? for iron rop«t (3) W = Cx3-00.-.C = \/yorC=y/H.^y'rorp.(entate9li»(ieB. (1) W = Cr'x4-00.-. C = \/^orC = »/""'i5f(»ri.longh.BteelropBs. 218 PRACTICAL COAL-MINING. These formulse do not allow for the weight of rope hanging in the shaft, and to correct this, a second formula may be employed. Let L=lead of full cage in tons. (2= depth of pit in fathoms. M = factor of safety. C= circumference of rope in inches. B-^ f I L_ _ (1) Then 0= / V5 _ d . for iron ropes. V M 1 "•1x2240 (2) ^ ~ ^ / _?. _ ^ .... for steel ropes. V M 1-1x2240 Examples. — Find the circumference of (a) a hemp, (6) iron, (e) plough-steel rope for a safe working load of 4*5 tons. /4*5~x 10 («) C=^ -- - = ^180 =13*4 inches for a hemp rope. /4 *5 X 1 0 {b) C=^ --- =^S0 =5*47 ,, ,, an iron rope. /4'6 X 10 (c) C=/y/ — ~ = ^11-25= 8-35 „ ,, a plough-steel rope. Or, by second formuls, supposing depth of pit was 150 fms. : — Ar 10 1-1x2240 Weight of Ropes. p I Let «;= weight of rope in lbs. per fathom. (I) Then w=<^x'26 for hemp ropes. } c= circumference of rope in inches. (2) k;=c'x'9 for steel ropes. The weight of rope in above calculations would be : m;=(18*4 )'x -25 =44*89 lbs. per fathom for hemp rope, and to =( 3-63)2 X -9 =11-90 ,, ,, steel rope. Strength of Cage Chains. -Let U7=safe working load in tons. D= diameter of iron in eighths of an in. (i-ths). Then w= — ■. 2*5 xM M = factor of safety (10 for cage chains). . '. D = *>^w x M x 2 *5. Example, — What size or diameter of iron should be used in cage chains for above calculations f D = \/4'5x 10x2-5 = 10*6 eighths or — = 1} in. diameter of iron. o WIHDmO GOAL. 219 To find the weight of chains, Let W=: weight in lbs. per fathom. D= diameter in sixteenths of an inch. Then W = D2x -21 ; for above size of chain W=(20J'x -21. =84 lbs. per fathom. The weight varies with the length of link, but for ordinary makes the above gives the average weight. Counterbalancing. — The load of a winding engine is often a very varying quantity, particularly in deep shafts, and the power of the engine cannot under such circumstances be utilised to the best advantage, hence the necessity of some compensating arrangement to equalise the load during the ' wind.' Balancing the load can be effected by different methods, such as by — (1) The chain and staple arrangement. (2) By the tail rope method. (3) By using conical or spiral drums. (4) By Koepe's system of winding. Chain and Staple Arrangement, — In this method of counter- balancing, a staple pit is required in addition to the winding shaft (fig. 220). The depth of this staple is such that when the cage is at the beginning of the wind, the heavy chain which is attached to the drum shaft, and which is used as a balance, will be hang- ing at the top of the staple ; its weight at this position will assist the winding- engine when most required, t'.e. at the start of the lift, and when the cages are at mid shaft the whole of the chain will have accumulated at the bottom of the staple. During the latter half of the wind, when often the load is a negative quantity, the chain will again be raised to the top of the staple ready for another wind. Thus during the first half of the wind, and when the load is greatest, the engine is assisted ; in the latter half, when the load is a diminishing quantity, the engine is retarded and brought more easily to a stop. The disadvantage of this method is, that it often requires a staple pit 40 to 50 yds. deep, involving considerable expense. Fio. 220. — Chain and staple balance. 220 PBACnCAI. COAL-MININ(J, Tail Rope MHhod. — In this system of balancing, a 'tail tope,' of the same weight as the wiading ropes, is attached to the bottom of each cage, and passes i-ound a beam, placed oci'oss the shaft, and below the level of the pit- bottom (see fig. 221). A pulley working in a shding frame was at first used in this method instead of a beam, but it docs not work so well, as the rope b apt to get off the pulley, or to pull it out of position. When the pit is deep do pulley or beam is required, the weight of the rope causing it to form a natural loop of itself. This syst«m of counterbalancing has been found to give good results, but it is most suitable for shafts that are compamtively free from cross buntons, pump rods, pipes, and other apparatus, although the writer has seen it successfully applied in rectangular shafts, where cross buntons are necessary. The tail rope should be attached to a bar of iron laid across the bottom of the cage, the strength of Uie bar being less than that of the rope, so that in case of accident the latter may give way rather than the rope. Vottical or Spiral Dmtnt. — This method of counterbalancing would bo one of the best that Fio. 221.— T«il could be adopted, but to obtain perfect balance, tope method. and at the same time to got a satisfactory degree of wear out of the ropes, the drums would often require to be 35 or 30 ft. in diameter, which would make them very heavy and expensive. Hence such drums are not much used, and V where they were employed, they have been dis- carded owing to accidents taking place by the rope slipping on the , drum. To pre- vent slipping, a spiral groove was sometimes turned on the drum. In many cases the rspuridnmiB. ??''*'> P"*^ ?" the drmn by riveting an angle iron on shell plates or an openwork frame, the angle iron forming a continuous spiral from end to end of the sloping Fio. 222.— GoDickl oi WINDING COAL. 221 portion of the drum (fig. 222). By this method it is almost impos- sible for the rope to slip. The drum is usually so arranged that several coils of the rope wind round the flat centre part of the drum. This enables the latter to be made smaller at the large diameter than would otherwise be the case. To find the ratio between the large and small diameters of such drums the following rule may be used : — Let a = full cage at pit-bottom. (= empty cage at pit- top. e= loaded cage at pit- top. Then{(a x z) - (6 x y)} = {(c x y) - (rf x x)] - '• x <2= empty cage at bottom. a; = diameter of small drum in ft. y= „ large axd ory = cxb £&ramf»2c.— Suppose full weight of cage at pit-bottom is 4 tons, full oa^e at top is 3 tons, empty cage at bottom 4 tons, and empty cage at top 1) tons ; let small diameter of drum be 12 ft^ ; find what diameter large drum would require to be under above conditions. Here a = 4, 6 = 1-6, c=:8, rf=4, and x=U. . ". y = Ml-ti) = 21-33 ft. . '. y, the diameter of the large drum, would require to be 21 } ft Koep6'8 System of Winding. — This system of winding was invented to secure a properly balanced load. Instead of a drum, as in ordinary winding arrangements, a large pulley is used, and only a single winding rope is required. The same rope extends all the way from one cc^e up over a pulley on the head-gear, round the engine pulley, back over the second pulley on the head-gear, down to the other cage, then to the bottom of the shaft, where it forms a loop, and lastly up to the cage from which it started. The friction between the rope and the engine pulley is sufficient to raise the useful load, which represents all the work required to be done by the engine, since the rope is balanced in every position of the cages. This system has never had any extended application for winding in Britain. At the few places where it was adopted, it has since been discarded for the ordinary arrangement. In workings it was found that the winding pulley did not give sufficient gripping power, and the rope was apt to slip, and Figs. 223, 224.— Koep^ system of winding. 222 rRACTICAL COAL-MINING. Fias. 225, 226.— Spring attachment for winding ropes. WINDING COAL 223 • allow the cages to run back. Another danger was that if the rope broke, both cages would fall to the bottom. To overcome those difficulties, a modification of this system has been adopted, in which two additional pulleys are used below those of the head-gear, and at right angles to them, over each of which a rope extends from one cage to the other. These safety ropes are meant to prevent the cages from falling away in the event of the main winding rope breaking. A balance rope is also- used, which is attached to the bottoms of the cages and passes round a beam in the pit-bottom. Seducing the Strain on winding Bopes. — As the greatest strain on a winding rope is at the moment of starting, various appliances have been introduced to reduce this as much as possible. One of the first methods was to put pieces of india-rubber below the * mingles, ' or plummer blocks, to give some spring to the pulley when the load is lifted. But rubber is a bad substance for this purpose, as it possesses a very small amount of elasticity, and soon loses the little it has, especially when exposed to the weather. Placing the pedestal on springs, like an ordinary waggon spring reversed, has been tried with much success for reducing the strain on the rope at starting to wind. Sprikg AttaehmerU, — ^At the Gerhard Colliery, near Saarbriicken, in Germany, a spiral arrangement is used for attaching the rope to the cage. The former is placed round a sheave a (figs. 225, 226), and the loose end is fixed to the rope by means of four clips. A bolt by 2^ in. diameter, runs through the sheave, to which two round wrought iron rods e of a diameter of 2 in. are attached at their lower ends. These rods are connected at the bottom by another strong bolt d. Upon this last bolt rests a plate of cast steel e, which receives the powerful spiral spring /. The upper end of the spring acts upon the wrought-iron plate /;, above which two hoops h are screwed. The ends of these hoops are formed into eyes, which by means of the bolt t. If in. diameter, are connected with the links riveted on the cages. The round rods k serve as guides to the plate e. When the cage is raised, the spiral spring presses against the iron plate under the hoops, and the cage is lifted gently. When the rope above the cage is loose, the rods c c descend perpendicularly on to the plate, and thus all jerking of the rope is avoided. Spring Coupling,— Another apparatus used for the same purpose is that known as the ' spring coupling.' Figs. 227, 228 show this apparatus. It consists of two plates a a, working on pivots, and two end plates b 6, connected by links c r, which are pivoted to both of these plates. The side plates are held apart by a spring d, through the centre of which passes a loose rod e, one end of which is fixed rigidly. When a sudden strain is put on the end plates a a, the side plates b b approach each other and compress the spring. As the strain increases, the resistance of the spring to compression also becomes greater and the compressing power of the links becomes less, so that a condition of equilibrium is attained. ■ 224 PRACnCAL COAL-MINING. Gage OuidfiS or Conductors. — Wood Guides. — The cage is directed in the shaft by guides, which may be made by either (a) wood, (b) iron or ateel, (c) wire rope or circular rods of iron. Wood guides are usually made of pitch pine, the size depending on the loads raised. For cages holding one tub the guides would be 4 in. x 3 in. or 4 in. X 4 in., and for double cages with two tubs, 6 in. x 4 in. or 5 in. X 6 in. The guides are cut into lengths of 12 to 30 ft., 18 and 24 ft. being lengths commonly naed. They are fixed to the cross Fioa. 327, 228.— Spring coupling. buntons in the shaft, and joined together as shown in figs. 229, 230, 231. Fig. 231 shows a common method of joining them by an ordinary ' butt ' joint, with a piece of wood 4 in. x 4 in. to stiffen them, 6ied at the joint by means of bolts having their heads counter-sunk in the faee of the guide so as not to catch the shoe, attached to the cage, in passing ; or very often an iron plate about ^ in. x 3^ in. is used with an ordinary butt joint as before (see fig. 230). A ' scarf ' joint is also used and an iron fixed as before, with bolte having their heads counter-sunk (see fig. 329). Wood guides are most suitable for rectangular sliafts in which cross buntons are necessary for their construction ) they are easily fixed, cheap at WINDING COAL. 225 firet coBt (about la. 6d. per cubic foot), but on becoming worn require frequent repairs and are very liable to cause accideuta. iTon and Steel Guides. — These guides are now very largely used. They are made somewhat in the style of an ordinary rail for surface use, and weigh from 40 to 60 lbs. per yard Great care is required in fixing these guides to fit them to the proper gauge, and to have all joints even and perfectly vertical, because if they are not well-fitted to begin | with, they give a great deal of trouble. Fig. 232 shows the ordinary method of fixing them ; each ' chair' should carry the weight of the guide above it, as they should not rest on one another, but a small apace should be ' left at each joint to allow for contraction and expansion. The space for admitting the guide into the chair is mjido a little smaller for the top side, so that a small portion requires to be taken out of the guide to admit it, the projecting f,(,b, 228, 230, 231.— Cage giuds*. parts acting as a support for it. These rail guides should be made of steel, as iron, having very much less elasticity, causes a greater degree of vibration in the cage, which is a matter of great importance in rapid winding. Briart's Mdlwd of Fixing Guides.— la this method of fixing steel FiOB. !32.— Iron guides. i single series of H guides, which is so common on the Continent, a mtders, 9 ft. 10 in. apart, divide the shaft. Each guide is 19'66 ft. long, which allows a slight play between the joints. Previous to being fixed, the buntons are carefully notched to receive the foot of the rail to a depth of 039 i . and to a width 15 PRACTICAL COAL-MINING. of 4-33 in. Figs. 233, 234 show the method of fixing the guides. Two steel glands a a secure the rail c to the buntous, one above and another below, and are made to grip the guide firmly by a pair of bolts 6 6 passing through them. To prevent any moTement, or the rails from getting twisted by the pressure of the glands, a block of cast Fioa. S33, 334.— Biurt'B method. iron, through wliich the bolts pass, is placed between the rails, and is furnished with a slight projection, which fits into a corresponding groove in the flange of the guide. This arrangement has been found to act very effectively. In passing through tubbing, the bunions are carried in boxes or shoes bolted to the internal flanges of the tubbing, the girders being wedged in position with wood keys. WIHDINO COAL. 227 Iron or steel guides are suitable for either circular or rectangular shafts, and always retj^uire biintons for fixing them ; they are much more durable than wood guides, but more expensive at first cost and difBcult to repair. When they get unevenly worn tlioy can no longer be repaired, and there is also a tendency for the circular head of the guide to get worn off if the cage shoe grips it too tightly. If properly fitted at first they will often last for years without giving any trouble, and require little repair. Bope or Bad Guides. — These conductors are very extensively used in cir- cular shafts where no buntons are required in their construction, and there can be no doubt as to their suitability. It must, however, be remem- bered that there should be at least 15 in. to 18 in. clearance between the comers of the cage and the walling to ensure safety in windiug. Cold drawn steel rods twisted together are often used in- stead of the ordinary rope guides ; they give greatly increased strength, and wear much better. They are mode up of seven to fifteen rods, with a total circumference of 2^ to 4j in., and weigh from 81 to 25 lbs. per fathom. The size used will depend on the load and strength re- quired. The conductors are fastened to a strong beam at the pit-head by means of five or six glands to keep them from slipping (figs. 235-238), or they may be fastened by a capping and strong eyebolta fastened with a nut and washer. At the pit-bottom they are kept tight by attaching weighta to them (fig. 235). This ia preferable to fixing them rigidly, as it allows Fia«. 235, !Sii, 237, S3S.— Hops guidM. 228 PRACTICAL COAL-MIKING. for expansion and contraction, which is often of considerable amount, the weight used being about 1 ton for 250 yards of conductor, although the exact amount required can only be ascertained by experiment in each individual case. The weight should not be in the form of a single solid block, but in the form of segments or 'cheese weights,' and used in much the same way as weights are used on a 'dead- weight ' safety valve. Some prefer to fix the guides at the pit-bottom and pass them over pulleys at the surface, attaching weights to the loose end. At some collieries they are fixed by a strong spring, to allow of the necessary expansion and contraction. The number of conductors used will depend on the load and upon the speed of winding, but in ordinary cases two guides are often used one on each side of the cage, while for heavy loads and quick winding it is best to have at least four guides, one at each comer of the cage. To prevent the cages from catching each other in passing, two imconnected conductors should be suspended between them; the space between the cages may then be as little as 6 in., but 12 to 15 in. is a better allowance. The advantages of using rope guides are : — (1) The first cost is cheap. (2) They are easily fixed and require few repairs and little attention, except oiling regularly. (8) Thev last much longer than wood or iron guides. (4) No buntons are required for fixing, and they occupy but little space in the shaft. (5) They are more flexible, and contract and expand more readily than rigid wooden or rail conductors. Cages. — These are made of different sizes according to the output required, the size of shaft, and that of the tubs used. The material employed in their construction is either wrought iron or steel, the bottom being often constructed of oak, but for large cages it is best to dispense with wood altogether, and to make them entirely of steel or wrought iron, as by this means their weight will be much reduced, which is an important point to keep in view. A good cage made of steel throughout should not weigh more than about two-thirds the weight of the coal raised, while a wrought-iron one should weigh about three-fourths of weight of coal rais^ per wind. A cage should be so constructed as to allow the greatest carrying capacity with the least possible weight ; the form selected should be such that the tubs can be readily placed in it and easily removed, while the whole construction should run easily in the shaft. Cages cost from £30 to J&35 per ton if made of wrought iron, and from £40 to £45 per ton if constructed of steel. Before cages are used they should have two coats of good paint, which will help to preserve them from corrosion in wet shafts, and particularly in pits where the water contains acid. Figs. 239, 240, 241 show the con- WINDING COAL. 229 atruction of cages for holding a single tub, this form shown being frequently used in Scotland, as they are easily and cheaply made. Figs. 243, 243 show a form of single-decked cage for two tubs placed abreast, a type much used in rectangular shafts. Fios. 23S, 240, 241.— Single oaga. Figs. 244-247 show two types of double-decked cages, in one of which the tubs are placed abreast, and in the other, which is usually more suitable in circular shafts, end to end. Cages with the tul» placed abreast are generally more suitable for rectangular shafts, where the apace is narrow compared with its length. Figs. 248, 249 230 PRACTICAL COAL-MTNING. Figs. 242, 243.— Single-decked cage for two tubs. l^^^Sl t^=EfSH=Hll Fios. 244, 245. — Double-decked cage for four tubs. WINDING COAL. 231 show the detailed construction of a cage for drawing mineral on an inclined sliaft. Gage Speeds. — The speed of the cage in the shaft may be anything between 15 and 40 ft. per second. The following are average speeds : — depth, 50 to 100 fms., speed, 15 to 20 ft. per second ; 100 to 150 fms., speed 20 to 25 ft. per second ; 150 to 200 fms., 25 to 35 ft. per second ; and for depths above 200 fms., from 35 to 40 ft. per second. Pit-head PulleyB. — Pulleys used on pit-head frames are usually made either of cast or wrought iron, or a combination of both, the rim and bosses being cast and the spokes constructed of wrought iron. The shape of the groove varies with the shape of the rope •*flfc«!*i > 9 Llmii^'Si^' t ^-'-' /^ />§' '6 I I I U. ►- s**'- • --< I I Fios. 246, 247.— Double-decked cage for four tubs. used. The size of pulleys will also vary between 6 and 20 ft. in diameter, according to the size of rope and drum used. Where wire ropes are used they should be as large as possible to avoid straining the rope by too sharp a bend, a common size being between 12 to 16 ft. in diameter. The diameter should, however, be in proportion to that of the rope used. For a steel winding rope 1 in. diameter, a pulley not less than 10 ft. in diameter is required, and for ropes from 1^ in. to If in., pulleys should be 15 to 20 ft. in diameter, while, as a rule, they ought to be About the same Eiize as the winding drum, 232 PRACTICAL COAL-MINING. Drams. — ^Winding drums are either cylindrical, conical, or spiral in shape, the first-named being the most common, and being usually constructed of two oast-iron cheeks fitted or keyed on to a wrought iron shaft, and lagged between the two cheeks with strong wood deals for the rope to coil on. Sometimes they are wholly constructed of Fios. 248, 249.— Cage for inclined shaft wrought iron or steel. Conical drums should have a spiral groove rimning round them, from the shorter to the longer diameter, in order to keep the rope from slipping. A spiral groove should also be used on an ordinary cylindrical drum to prevent excessive side friction between the coils of rope when winding, which will increase its life (see fig. 250). Drums ought to be made as light as possible so as to WINDING COAL 233 e time minimise the inertia at starting. Good, strong, and at the si light dnima are beet made of steel. The siiw of drum lised will greatly depend on the size of engine erected for winding and upon the size of the rope, but it is a mistake t« use very lai^ drums, as large diameters de- crease the efficiency of the engine. In winding, speed requires to be got up quickly each wind, and with large drums this will not be so easily attained as with drums of smaller diameter. The drum may be increased 1 ft. in diameter for each additional 2 Ihs. weight in the rope per fathom. Fio. 250,— Drum. Flo. 261.— Dmm with block and bnka. Drum Brakes.— It is desirable that a good reliable and efficient brake should be at- tached to the drum of all powerful high-speed winding engines. The power should be applied as near to the centre of the dmm as possible, and a large leverage, from 160 to 200 to 1, given. The ordinary block brake is very efficient, and is largely used in Scotland (fig. 251). In this brake two blocks of wood, generally elm, are brought into contact with an iron ring fixed and the power applied by Fio. 252.— Brake device. either on the centre o 234 PRACTICAL COAL-MINING. an arrangement of levers that can be worked either by hand or foot by the engineman. The type of brake shown in fig. 252 is much used in some dilstricts of England. It is one which is arranged underneath the drum, and there is little friction when the engine is at work, as when released it immediately frees itself of all contact with the brake *ring.' This brake is applied by a toggle joint arrangement^ and is arranged so that it can be worked either by hand or steam power. It should be made from well-seasoned blocks of elm or oak wood. Another form of brake — known as Bums's brake — one that gives good results, is very powerful, and has also the advantage of being simple in construction, is shown in fig. 253. In this brake a single block of wood is fixed to a long lever and applied to the bottom of the drum, the leverage being in the ratio of 200 to 1. In the block holes are sometimes bored and filled with sand, which renders the brake much more effective. Safety Hooks. — In no class of work about a colliery is there more liability to accident than in winding, and yet such accidents are happily rare, no doubt owing, in a large measure, to the careful =i H Fio. 258.— Bnrns's brake. handling of the engines by those in charge. When it is considered, however, at what speed they have to be worked, and the number of times the cages have to be raised and lowered even in the course of one shift, it is obvious that an accident due to overwinding may easily occur even with the most careful engineman, as some portion of the engine may get beyond control, and prevent it from being stopped at the proper position. It was to obviate the effects of overwinding that safety hooks, which have been applied with much success, were invented. Many colliery owners do not, however, use these hooks or other safety appliances, because they are likely to get out of order and not act when required, and more confidence is placed in having good reliable men at the engines than in any mechanical contrivance. There have, doubtless, been cases where safety hooks have not fulfilled expectations, and where they have even broken when an overwind took place. But this may happen with any piece of machinery, particularly if it is not properly looked after and kept in good working order. If, on the other hand, the use of safety hooks renders men's lives safer in the event of an over- wind, there is no good reason why they should not be c^Jopted at all collieries. WINDING COAL. There is a large variety of safetj hooks before the public, but the principle upon which they act is practically the same in all. lu some the rope is simply releoaed when the cage is overwound, and in others the rope is released and the cage held fast simultaneously. Walker't Detaching Hook. — This is one of the most efGcient safety Fios. 2G4, 255.— Walker's detschiug hook, hooks in use. Its principle will be understood from figs. 254, 255. The book consiata of a pair of jawa D D working on a centre pin. These jaws are held together and made to retain the strong action bolt ill the rope shackle A by means of the clamp K, which is kept in position by the copper pins (, and the outward pressure due to the weight of the load. In the event of an overwind, the jaws pass 236 PRACTICAL GOAL-MINING. freely into the riog C, which is a fixture, but the flanges E of the clamp H coming into contact with the ring C, as in fig. 254, is held stationary while the jawa are pulled through, with the result that the copper pins I are sheared off, and the hook jaws F F are forced open by their lower portions being drawn into the clamp, in which position they are firmly locked, as shown in fig. 355 ; the rope then passes over the pulley, and the load remains suspended. This hook being made without side plates, is not liable to get fast, is simple in construction, and can be quickly and easily re-connected. West's Hook. — This hook is also simple in arrangement, and is Fio. 268,— Weat'» hook. composed of the body A (see fig. 256) and two sliding catches B and B', 6tt«d with a copper releasing pin C and a locking bolt D. When an overwind takes place, the wedge-shaped portions of the sides B B' come in contact with a fixed plate E, and are forced into the outer steel Iwi A, whilst the opposite ends are forced out as in the figure, allowing the shackle and pin to be liberated and held suspended on the plate E. king and Hwnhle'g Hook. — This hook consists of two outer plates a a and two inner plates, all of which are pivoted upon a strong centre pin b (see figs. 257, 258). The winding rope is attached to the top shackle d, and the cage and chains to the bottom shackle e. WINDING COAL. 237 The wrought-iron catch-plate g^ through the centre of which passes the winding rope, is securely fixed to the head frame immediately under the pulley wheel. In the case of an overwind, the hook is partially drawn through the centre hole in the catch plate, until the bottom jaws of the inner plates of the hook come in contact with the underside of the catch- plate, when they are pressed inwards, shearing the copper pin c, causing, by the same action, the upper jaws to extend, thus releasing the rope, and, at the same moment, the hook locks upon the catch- plate. The latter is so constructed that there is just sufficient space between the lower jaws and the locking jaws for the catch-plate to insert itself, hence the hook cannot be sufficiently detached through the catch-plate to allow the locking jaws to get on the top side of the plate. As soon as the under jaws are forced out, the hook is Fios. 257| 258. —King and Humble's hook. therefore locked on the upper side of the catch-plate. King and Humble's hook is also furnished, in case of an overwind, with an automatic lowering arrangement which consists of an elongated slot just above the centre pin. When an overwind occurs, the rope is brought back over the pulley to the hook, for which a spare shackle is provided. This is passed through the rope shackle and down over the hook to the lowering slot, whereupon the rope is slightly tightened, which causes the inner plates of the hook to close, and the hook with the cage attached can now be lowered on to the pit keps. Safety Cages. — Safety hooks, such as those described above, are meant only to prevent accidents in cases of overwinding, and afford no security against accidents resulting from the rope breaking while the cage is running in the shaft. To guard against this, innumerable safety cages and appliances have been invented, although few of them have proved to be of any real value in practical working. 238 FBACnCAL OOAL-tOKIMa. On the Continent, aa in Germany, the use of safety cages ia enforced by law ; in Britain, however, anch sppli^ncoB arc not compulsory, and among coUiery proprietors, at least in their present form, find but little favour. Moet of tbem depend for their action on a grip or spring which ordinarily is not in contact with the guides, but which, in the event of the ropo breaking, is released, and clutches them in order to prevent the cage from faUing. While they may be of some use where winding is carried on at low speed, they are practically nseleaa at moet modem collieries where the speed is often very high. In such cases they often fail to act on an emergency, or allow the cage to fall back with such velocity that the guides are greatly damaged or even broken, and the cage is precipitated to the bottom of the shaft. If men are in it, the shock is likely to be so great as to either pitch them out or dash them t^inst the top of the cage. Quite recently an accident occurred in a mining district in Germany, with one of these pro- tected cages, supplied with safety grips and a controlling lever worked from the cage itself. Notwithstanding these pre- cautions, and the fact that every- thing was in working order, the appliances proved useless, and gave way, with the result that the nine men in the cage were killed. Fio». 269, 2B0.-A4iuiting screws for The best preventive against winding ropes. such accidents occurring is to use only the best quality of winding ropes, to give them careful treatment, and to inspect them frequently. Adjusting Sertwe. — In ordinary practice the length of winding ropes is adjusted by increasing or diminishing the spare coils on the drum and by relixing them or cutting a portion off and re-capping. By such methods it is, however, very difficult to secure exact adjustment with- out mnch labour and care. To obviate this, adjusting screws have been applied. Figs. 259, 260 show the construction of these screws. They consist of a strong steel rod a, terminating at each end in an eye. The shackle at the lower end of the rope is attached to the upper eye. A round block b, with a hole in each end large enough WINDING COAL. 239 to admit of the easy passage through it of the screws ce, ia placed in the lower eye. Screw c, 2^ or 3 ft. long, with strong threads and an eye at their lower end, and provided with nuts d^ screwed on to them, are passed through each hole in the block, and the nuts e are then screwed on to them from above. Each nut e, while resting on the block, supports its own screw. Two triangular plates //, with a hole at each angle, are attached, by means of pins passing through two of their holes, to the eyes at the lower ends of the screws, which they then enclose between them. The third eye in each of these plates hangs vertically below the steel rod which supports the block. A third triangular plate g, with three holes, one at each angle, is inserted between the two first, and a pin is passed through one of these holes and through the unoccupied holes in the two plates above it. Two short pieces of chain are attached to the remaining holes in the lower triangular plate by means of shackles, the cage being attached to these chains. The ropes can be adjusted in a very short time, without much labour, by means of these screws.* Cage Prope or Keps. — ' Keps ' or ' props ' are required at most collieries, as a rest for the cage and to keep it in position during the changing of the tubs. At some collieries no keps at all are used, the engineman maintaining the cage in position by applying the brake to the winding drum until the tubs are changed, by which means the ropes are said to last longer. It is also claimed that there is less liability to accident, owing to the absence of 'keps,' which require to be opened and shut every time the cage comes to the surface. Unless the cage, however, is brought to a dead level with the plates on the pit-head, the rope undergoes a good deal of jerking during the opera- tion of changing tubs. The ordinary form of ' keps ' usually consists of four legs pivoted at right angles to each other, and attached to a lever for opening or shutting them. They are generally allowed to swing out while the cage is running in the shaft, and are automatically opened by the cage itself, when it arrives at the surface, but they have to be opened by hand when the cage is about to make its descent. The commonest form of keps, made wholly of iron, is shown in fig. 261. Stau88 Keps. — In these keps (figs. 262 to 265), the invention of a German engineer, the cage is held firmly and securely in position when it arrives at the landing stage, and is released again for descent into the shaft, without the necessity of lifting a foot or two, as with the ordinary form, to allow of their being first drawn back, which often causes a sudden jerk or strain to be given to the slack rope. When the cage is to be held fixed, it rests upon the surface y of the catches or tappets c ; these catches resting upon the part x and against the pin b, and being held fast both in a horizontal and in a vertical direction. The latter function is discharged by the bell-crank 6, which presses against the shaft d ; whilst horizontal movement is * Lectures on Mining^ by Prof. Wm. Galloway, p. 7. PRACTICAL COAL-MININQ. -2-- if FlQ. 2fll. — Arrangement of keps. Floa. 282, 363.— Strauss kcps, shut, with cage resting. WraDING COAL. 241 prevented by the crank/, which preascB aguiuat the shaft /, through the bolt i, of the lever k. In this way the steadiness of the cage is secured, and displacement is prevented. The hand lever A presses the lever k, when in this position, down against the block m, which is fixed to a casting ii, bo that side play is also prevented. When k b brought into the poeition shown in fig. 265, and indicated by dotted lines in fig. 264, i is brought to the position »", and ft to ft', by which cage means the catches are withdrawn from under the cage and are lowered at the same time, so that the latter can descend the shaft. When the cage again arrives at the pit-mouth, the hand lever A is pushed back into its first position, the catch e projects, and the cage is secured. The advantages claimed for these keps are : simplicity of con- struction and working, and & saving in ropes and engine-power, the b Fioa. 264, 265.— SttauiB ksps, open. short jerks which injure the former in lifting the cage before it descends being done away with. Hydraulic keps are used on the Continent, but they are apt to get out of order, and are not reliable, owing to their complicated nature and to the water freezing in the pipes in winter. Fig. 266 shows the construction of these keps. Instead of four rigid arms (as in ordinary keps) there are four short cylinders, ft ft, each provided with a stufBng-box and plunger e. Hinged to the top of each plunger are movable pieces d d, which take the place of the rigid arms in ordinary keps. The four movable pieces are connected ti^ether by means of rods e e and levers //, and move inwards and outwards like the arms of ordinary keps. The cylinders are connected to each other by a pipe g, common to all four, which also communicates with the cylinder of an accumulator. There is a stop-cock on this pipe which can cut off communication with the accumulator. Suppose the four plungers to be in their highest 16 242 PRACTICAL COAL-HININO. position, and the Btop-cock shut as in the figure. The loaded cage ascends the shaft, and reaching the surface pushes the four movable pieces dd aside, passing up between them. The latter immediately fall bock, and the edge is lowered on to and arrested by them, and the liquid in the cylinders, having no outlet, prevents the plungers from descending. When the full tuba have been replaced by empty ones, the stopcock is opened, allowing the liquid to pass into the accumulator until the movable pieces d d are clear of the cage. Automfttic Apparetm.^In the case of an overwind much damage is often done, which cannot be prevented even by the use of detaching safety hooks, the objects of which are to prevent the cage from falling back in the shaft. Appliances are also used to prevent loss of life if the cage happens to get overwound. In Germtuiy every winding Fia. 336. — Hydnnlio heiia, engine requires to be fitted with a steam brake which enables it to be brought to a standattll at once when required, even when going at full speed. To make the brake self-acting, a hydraulic arrangement is some- times used which the cage, when lifted too high, actuates itself. About half-way between the winding drums and the shaft, a pump, with reservoir and accumulator, supplies pressure to a length of piping leading M the shaft ; and further, to a return length of piping leading back to the steam brakes on the drum. A vulve at the abaft permits the pressure from the accumulator to be carried further only when it is raised by a lever, which, in case of accident, the cage itself will actuate. The pressure thus communicated to the return length of piping acts on a vertical cylinder working on the accumulator principle, and by a rod and systom of levers, may either act on the piston rod of the steam brake direct, or, by actuating the slide valves, admit the steam to the brake cylinder in the usual manner. WINDIKO COAL. 243 The Visor. — This apparatus also has been designed for the purpose of preventing overwinding, and has been in use at the pits of the Wigan Coal and Iron Co., Ltd., since 1888. The governors are driven by suitable gearing from the crank-shaft of the winding engines, as is also the worm-wheel shaft. The latter makes, approximately, one revolution per wind, and carries beaked cams, which can be adjusted to the required positions. As the speed of the engines increases, the governors rise, and move, through the medium of levers, two vertical arms with attached tappets bringing the latter into the line of revolution of the cams on the worm- wheel shaft. Towards the conclusion of the winding, if the speed of the engines is reduced suitably, the governors fall and bring the levers, with hooks attached, out of the path of the cams on the worm-wheel shaft, and into position, so that the cams pass without making contact. If through any cause the speed of the engines is not, however, suitably reduced as the cages approach the top and bottom of the shaft, the governors fail to collapse, and one of the beaked cams on the worm-wheel shaft makes contact with one of the vertical levers, the sliding frame is drawn up, the pawl raised out of the notch in the bar in the bottom of the frame, and the weight at the other end immediately falling, upsets the propped and weighted levers, and applying the steam and foot brakes shuts off the steam, and thus arrests the engines. The apparatus begins to act about two or three revolutions from the top, giving time to pull up gradually, but if the speed of the engines is maintained too long, the visor comes into operation. Size of Winding Engine. — The calculation of the proper size and strength of the various parts of a winding engine belongs more to the province of the mechanical than to that of the mining engineer. Nevertheless at most of the examinations for colliery managers' certificates, questions on the sizes of winding engines are set, often with very insufficient data to work on, and sometimes with such as no mechanical engineer would accept. The load which an engine has to overcome is of two kinds — viz., a * dead load ' at the beginning of the wind, and a ' live load * when the cage is in motion. It requires more force to move a dead load than to keep a live load in motion. The simplest method of calculation is to take the work done in the shaft during one revolution of the drum, at the worst part of the wind. This will be at the moment of the cage coming to the surface, at the moment when the cage with the empty tubs has landed in the pit-bottom, and before the full cage has been brought to rest by the keps, so that the engine has the full weight to support without deriving any advantage from the descending cage. To leave sufficient margin the load may be taken as equivalent to the combined weights of the coal raised, the rope, and the empty tubs. 244 PRACTICAL COAL-MINING. The diameter of the cylinder may then be oalculated from the equation, D^ X *7864 xPxLx2xE = Wx circumference of drum, . W X cir. of drum or D-V. 7854 xPxLx2xE When D= diameter of cylinder in inches. P= effective steam pressure iu lbs. per sq. in. L= length of stroke in feet. £ = modulus or efficiency of engine (taken at ^ for coupled engines). G= circumference of drum in feet (diameter x 3*1416). W =s weight of load in lbs. (coal + rope + tubs). Example. Calculate the size of winding engine required to draw 500 tons per shift of eight hours from a depth of 250 yds. What length of stroke, steam pressure, and size of drum would be required 1 Tons per minute = ^^^ = 1 '04. ^ 8x60 Suppose the speed of cage is, on an average, 20 ft. per second. Then duration of wind=^?P*i2l««*=?-^» = 37i seconds. Speed of cage 20 Allow for time to change tubs at top and bottom (say 15 seconds). Total duration of wind =37*5 + 15 = 52*5 seconds. Calling this 53 seconds to avoid fractions, the load of coal raised per wind _l'04x53 60 = '91 ton, or 18*2 cwts. Suppose that two tubs are raised each wind, each tub holding 10 cwts. of coal, and weighing 4 cwts. when empty ; 4x2=8 cwts. Take the weight of cage at three-fourths the weight of coal raised = 13*8 cwts. , Then coal + tubs + cage =18 -2 + 8 + 13 "8 = 40 cwts., or 2 tons. Then to find the circumference of rope as a preliminary to finding its weight — C = ^'^^ = ^^ = 2-6S in. (say 2-« in.) W, in this case, being the total weight just found (2 tons). Weight of rope in lbs. per fathom=C x '9 = 5*99 (or 6 lbs. per fathom). .\ Total weight=6 X ?|?=750 lbs. Allow the effective steam pressure to be 50 lbs. per sq. in., and the diameter of drum to equal 150 x diameter of rope, ^ 2*6 X 150 JQ.3 J J ^^ diameter. 12x3*1416 ^ WINDING COAL. 245 Then, applying the formula given above, — D* X '7864 X P X L X 2 x E = W x circumference of drum D«x-7854x60xLx2x | = 1(18-2 x 112)+ (8x112) + 760} 11 x 8-1416 D« X -7864 x60xLx2x-8= {2038 "4 + 896 + 760}ll x 8-1416 D«xLx60x •2=1842-2x11 r,. T 1842-2x11 60 X -2 =2026*42. The length of stroke should be 2 to 2^ times the diameter of cylinder. Assume a stroke of 4 J ft. Then D«=???^=460-81 ; 4-6 and D= V460-81=21-2 in, (or 22 in.). From the above calculation, the size of engine required would be a pair of coupled horizontal engines with Cylinders 22 in. diameter ; Length of stroke 4) ft., working with an Effective steam pressure of 50 1m. per sq. in. ; and Diameter of drum 11 ft ; the cage being taken at 18*8 cwts., and the two tubs at 4 cwts. each, with a circular steel rope, 2*6 circumference, weighing 6 lbs. per lathom. This method of calculation is not, of course, ffiven as theoretically correct, but it will give an approximately correct answer to tne question. Professor Merivale gives the following formula for calculating the size of cylinder when the engine is counterbalanced : — <"*?) ^^ LP Where L= twice the length of stroke in feet. C= circumference of drum in feet. W = weight of coal per wind in lbs. A = area in sq. in. of two cylinders ; or half the area of cylinder if there be but one. P= maximum pressure of steam. Taking this formula for the above case — 11 X 3*1416 X ( 2088*4 + ????1*^ „, ^ ^^^^ ^ V 2 /_84*6x 8057 6 4*5x50x2 " 2250 =234*41 sq. in. .-. D = v/^^ = 1 7 -8 in. , diaww^ 0/ cyWtufer. The size of winding engine required can also be worked out in the following way: — Mxample, — What diameter of cylinder would be required to raise 1000 tons of coal from a depth of 200 fms. in eight hours ; the tubs 5 cwts. each, and carry 14 cwts. of coal, 4 tubs beine raised on each cage, the latter weighing 40 cwts. ? The effective steam pressure is to be 60 lbs. per sq. in., the stroke of engine 5 ft, and the diameter of the winding drum 16 ft. Tonsperhour=15??=:125, winds per hour=^^^ = 44*6, or 45 for con- ^ 8 4x14 venience. Time per wind = -?-^— =80 seconds ; and assume the time taken to 45 246 PRACTICAL COAL-MININO. change the tnhs is 20 seeonds, then the actual time occupied in windins will be 80-20=60 seconds, and as the shaft is 1200 ft. deep, the average speea of cage 1200 will be - - =20 ft. per second. The maximum Telocity will be about double 60 '^ ■' this, or 40 ft. per second. The time in which this Telocity is obtained may be taken as fth of the total time of winding, or 8*55 seconds. The circumference of rope required.* VL _ / 5-8 ~ _ / 5-8 ^ 4 D ^/± _200 \/ 'A-'OSl M 1-1x2240 'V 10" 1 1x2240 4-25 in. Weight of rope per fathom = C x *9 = (4 *25)> x -9 = 16 *S lbs. If the head gear is 60 fL high, then the total weight of rope is 210 x 2 x 16*3=6846 lbs. Let W= weight to be set in motion ; two cages, coal, empty tubs on cage, two winding ropes from pit-head pulleys to pit-bottom. y= greatest velocity obtained, uniformly accelerated from rest =40 ft. per second. ^=g|ravity=82*2. t=time in seconds during which Y was obtained =8*55 seconds. L= unbalanced load on engine =coaL P= effective steam pressure in cylinders =60 lbs. per sq. in. N = number of cylinders = 2. s= space passed through by crank pin in time i, e=§ constant to reduce angular space passed through by the crank to distance passed through by the pbton during time t, A = area of cylinder in square inches. D= diameter of cylinder reouired. /= allowance for friction of engines, etc, taken at 20 to 80 per cent. (a) The greatest work the winding engine lias to do is to get the mass W into a certain velocity, uniformly accelerated from rest. This work is difficult to calculate properly, for to do so the energy required to set the winding drum and pulleys in motion would have to be accurately ascertained. To allow for this energy to move these parts, the mass W has been taken to include the weight of the two winding ropes and the two cages. WV Resistance due to gravity and inertia = — . WV Vi WV Work done in overcoming resistance = — x -=- = -::- • (6) To raise the unbalanced load L, distance passed over in time t, WV« V^ Workdoneinft,lbs.=LxX? .•.A=--^-— - 1- 2 PxSxNxC If the load is baknced, L=4 x 14 x 112=6272 lbs., and W = 24,818 lbs. In time t the drum will make about 2*5 revolutions, . '. S = 2'5 x 5 x 8*1416 = 39*25. -^" ' 60xS9-25x2xi| -M5 17. Allowing 20 per cent, for friction, A = 535*17 -I- 107*03 = 642*20, and n - /642*20 =28*4 in. The size of the winding engines would therefore be •7854 28*4 in. diameter with a 5-ft stroke. * See formula for calculating size of winding ropes, pages 21 7, 218. OHAPTEB XI. HAULAGE. Glassification of Hethods. — The different modes of haulage employed underground may be classified as follows: — (1) Manual labour; (2) horse haulage; (3) self-acting inclines; (4) mechanical haulage by stationary engines placed either at the surface or underground ; (5) electrical or compressed air locomotives. Haulage Boads. — ^There is hardly anything of greater importance to an effective system of underground haulage than the laying down of the road. A good road when properly constructed should last as long as the colliery without entailing a great deal of repair or expense. On the other hand, a badly arranged and badly laid road will cause continual trouble and anxiety and entail great expense for repairs, so that it will cost far more in the long run than a good road, to lay down which may, at first, be a little more expensive. Baila. — The different rails in use are of three patterns, the flat- bottomed made of cast iron or steel, the * bridge ' rail made either of wrought iron or steel, and circular-head rails usually made of steel. Flat-bottomed rails made of cast iron with side flange were, at one time, almost universally employed, but the pattern of tub wheel required with this descrip- tion of rail occasioned so much friction, that it is being almost entirely abandoned in favour of the newer and more efficient circular-head or T-rail, except in old collieries where there are large stocks of old rails which it is desirable to use up. The newer kind of rail gives the minimum of friction, is easily laid, and, when made of steel, lasts a long time. It generally weighs from 14 to 20 lbs. per yaid according to the size of tub used and the weight of load. For main haulage roads, the heavier sections should be selected. 247 I I t . I Fi08. 267, 268.— Section of nils. 248 PKACTICAL COAL-MINING. Friction of Bails. — The force required to overcome friction is usually estimated at — 8 to 10 lbs. per ton on a surface railway (tH). 82 „ edge of T-rails underground (^). 70 ff flat-bottomed or tram-plate rails underground (^). Method of Laying Boads. — Where a large amount of coal has to be hauled over a road, the rails ought to be well laid, on some such system as on a surface railway, with joints * fish-plated' and rails well keyed and with plenty of * chairs.' On the best haulage roads the rails are sometimes laid on longi- tudinal sleepers, which are held together by cross sleepers, with the joints of the rails fish-plated. The longitudinal sleepers are often ordinary white pine planking 9 in. x 3 in., and the cross sleepers 5 in. X 1^ in. Wrought-iron and steel sleepers are also used in place of the ordinary wooden sleepers. Laying roads with iron or steel sleepers naturally costs a good deal more than when wood is employed, but the greater durability and stability more than com- pensate for the increase in first cost. Figs. 269, 270, 271, show the method of laying such roads, and will require no further explanation. Gauge. — The gauge will depend upon several considerations, such as whether the wheels project beyond or are under the body of the tub, the inclination of the seam, etc. It may vary from between 18 to 36 in., 24 in. being a common gauge. Narrow gauges are most suitable for flat seams, but where the inclination is great the gauge should be increased in proportion. The writer has seen a gauge of 36 in. employed where the inclination was between 30* and 45**. Tubs. — These are variously called * trams,' * corves,' 'hutches,' or ' tubs,' in the different mining districts. The body is usually rect- angular in shape, but sometimes they are semicircular at the bottom, which increases their capacity for a given height. The design and size of tubs used will be governed by the varying conditions under which they are required to work, such as the thickness of seam, height and inclination of roads, and whether manual or other kinds of haulage are most largely used. For thin seams where manual labour is used to any considerable extent for haulage the tubs should be made of small capacity and weight. A tub to hold 10 to 12 cwts. should not weigh more than 4 cwts. if constructed of wood, or 5 cwts. if of iron. The capacity varies greatly, and may be anything between 5 and 40 cwts., but an average size is from 10 to 15 cwts. In the South Wales coal-field tubs holding 30 to 40 cwts. are often used, while in some of the thin seam collieries of Somersetshire, and in Scotland, tubs holding 7 to 9 cwts. of coal are common. The advantage in having large tubs is that fewer windings at the*pit shaft need be made per diem for a given output, and that their capacity is large in proportion to their weight. On HAULAGE. 249 the other hand, they are clumsy to handle, and, it derailed, are difficult to place on the rails again. On the whole, a tub of medium capacity, i.e. 12 to 15 cwts., is to be preferred, as it can be moved about easily and lifted on to the raib by one man when neceaaary. Matei-ialn of Oonstruction. — ^Tuba may, as has been stated, be constructed either of wood, wrought iron, or steel. Opiniooa differ among mining men as to which of these materials is best. For light loads w(x>d is very commonly used, and it has the advantage of Figs. 369, S70, 271.— Method of l>:ring mil^ being cheap and light, while the cost of maintenance and repair is leas than for steel, and leaa akilled, t.e. cheaper labour is required for constructing and repairing wooden than for iron or steel tube. Again, it not infrequently happens that even in the best regulated collieries a train of tubs breaks away on inclined haulage roads, and wbeo such an accident takes place, the tubs will be more or leas smashed and broken. If made of wood they can soon be re- paired, even although they may be badly damaged, whereas if constructed of wrought iron or ateel they would be so twisted and 250 PRACTICAL COAL-MININO. bent that the work of a skilled blackamith would be required for their repair. In thick seams Ijing at a comparatiTel; small inclination, iron or steel tubs are preferable, especially if the load is large (20 to 40 cwts.). Figs. 272, 273, 274 show the construction of a tub designed by the author and built of wood. The framework is made of two ' trams ' of larch wood 4 J in. x 3} in., held together by oak ' starts ' 3 J liLxlJ in., and further strengthened by two iron rods 1 in. diameter. The body is of larch cleading 1^ in. thick, bound at W~!T bMt w rr *B^ 1 J '" t 1 J-, p. « W.,' : »■•» m i :- ;-HJ- 1 '•- „ ,<.-Jt: i E 3 plpf^ J Fios. 273, 273, 274.— Details of ooQBtnutian of woodan tub. the sides and ends with pieces of sheet-iron angle ^ in. thick. It is also bound round the top with a band of wrought iron. The capacity is 9J cwts. when filled to the level of the sides, and about 12 cwts, when heaped up above them. The cost of such a tub would be about £2, 15s. or £3 complete. Figs. 275, "276, 377 show a tub constnicted of steel aides and ends resting on a wooden frame. The latter is of larch held together by oak 'starts' 4 in. x 2 in. The sides are of steel j in. thick, and angle iron 2^ in. x 2J in, x j in, running round the bottom, and also at each comer, m order to bind the sides and ends together. HAULAGE. 251 The capacity of such a tub is 10 cwts., or 12 to 14 cwts. when heaped. The estimated cost is £4, lOs. Arrangement of Pit-bottom. — The first considemtion in any system of haulage is to have the pit-bottom laid out so as to best accommodate the tubs as they come and go. Many pit-bottoms are too confined, which may be a saving in first cost, but is never satisfactory in working. It should be so arranged that all the empty tubs can be taken off the cages at one side and the full tubs Osk tra\ns 4ift«3«> €: '^it^^,^a2. I ^o/l(«/n \o^ Tup ! • SimmJ K fhicU ICSI '51* • • • I r.'^TJ •__;^,L- .1-1.. 'j'a;i'Aa :d Fi08. 275, 276, 277. —Construction of steel tub. placed on at the other. Where it can be carried out^ this is the most satisfactory arrangement. Figs. 278, 279 show the arrangement of the pit-bottom at Eamock Colliery. Here the coal is raised from two levels, and these are so arranged that both decks of the cage can be charged at the same time, without the cage being moved. Fig. 278 shows a section of the shaft which more clearly explains the working. On the top deck. Ell coal is caged, while the lower deck is reserved for coal from the Main and other seams. To carry this out the lower level had to be formed in the strata above the Main seam, and a stone mine driven at an inclination in order to catch the coal. Fig. 279 shows the plan, which will be readily understood. On both sides of the pit-bottom there are double roads for full tubs and a road for empties. On the side A, which is worked by main and tail rope, the road for the empties dips away from the shaft for a certain distance at a gradient of 1 in 50 and then rises to the level of the other road at an mclinatiou of 1 in 30, so that no labour is entailed 252 PRACTICAL COAL-MININQ. in pushing the empty tubs forward to the desired position. The two full roads on each aide ate constructed to hold about 80 tubs. From the high to the low stage a by-road is formed, so that if there is not suiGcieiit coal coming in to keep the low deck, going, a train of tuba can be run down from the high level A to the low level B. The whole arrangement works very well, over 1200 tons being often raised in eight hours, with four tubs on each cage. Of course this arrangement would not suit in every case, but it may be taken as an illustration of a well-planned pit-bottom. Haulage. — Manual labour. — The method of haulage by men and boys can only be employed with advantage where the drawing roads are of moderate length and comparatively level, and where the tube are small. If the length of road is great, or the inclination high, it is the most expensive system that can be adopted, and in any case I i I Fia. 27S. — ElevatioD of pit-bottom. it is always better, where the height of seam will allow, to bring the tubs direct from the face by means o( ponies or by some other method of ttaction. Manual haulage should therefore be confined to short distances on level roads. In some small collieries where the seams are thin and the roads flat, it is often the only method employed for hauling the coal from the faces to the pit-bottom. Horsf TraeHmi. — Haulage by horses is employed more or less in nearly all collieries, there being sometimes 100 to 150 horses under- ground. If the inclination of the roads is not too great, it is often an economical and convenient form of haulage, especially if there is a slight inclination in favour of the load towards the pit-bottom. A horse is capable of exerting a tractive force of 1'20 lbs., when travelling at the rate of two to three miles per hour, and can keep this up for a period of ten hours, which enables it to draw 24,000 lbs. or HAULAOX. 253 10 tons for a distance of twenty milea, or 200 tons for a distance of one mile per diem. Two- thirds of this eatitnate is a fair average of the work which a horse usually perfonuB. The mileage depends greatly on local circumstances, but on moderately level roads horses ought to travel fifteen or sixteen miles per day, and in roads dipping 1 in 20, eight or ten miles per day, if the roads arc, in each case, in good order, with long runs and few stoppages. Horte UuaJn. — ^The moat economical form of horse road is where the work done, in drawing in an empty load, is equal to the work done in taking outa/u/f load; which for edge rails should be an inclination of about I in 1 40, or J in. per yard, in favour of the full load. When F = friction of full load, /= [rictioD of empty load, and O and g=grsvitj due to full sod empty J loads respectirely, £ F-0=/+ff. £ If 1 = friKtiaii representiDg gradient, A H = heLghtarinclineabi)ve horizoDtol, ^ L = l«ngth of incline, * W = veight of full load, J w= ,, empty load, b _H „ WH. I. I=2orG- KxatapU. — What shoiild ba the gntdlont for a horse haulage road, if the load conslBta of 12 tuba, each holding IG cwt«., and weighing Ci cwta. when empty, allowing ^ for friction ) /12xl6\ /12xB\ , \ 70 M 70 j *" (12xl6) + (I2x6) 180 80 IflO - 60 _ 70 "70 . 70 _1-71 1 180+60 2*0 210 "nr" at 1 in 140 (the gradient required). FfMing of Horees.^Vh'is forms one of the heaviest items in the keeping of horses under- ground, as a fair-sized horse will cost IDs. to 254 PBACTIGAL COAL-MINING. 1 2s. per week for food and bedding alone. The aim is to keep horses in the best possible condition at the minimum of cost, and this can be easily accomplished if the right feeding-stuffs are selected. Formerly the feeding consisted chiefly of boiled food, composed largely of beans, barley and bran, along with dry hay. Now it has been pointed out by qualified authorities, that bran has little or no feeding value unless as a laxative, and that barley and beans should only be used sparingly. Nearly all collieries now adopt dry feeding, or 'chop,' as it is termed, for the horses, this being found to keep them in harder and better condition than soft or boiled food. The latter, however, has its place, as animals, like men, appreciate a change, and this may be given at least once a week with advantage. Some green food during summer will also be relished, and is beneficial. The following * chop ' is sometimes given : — Cut hay, .... 8 cwts. Oats, Beans, Indian corn, Peas, 5 „ 21 n 2i „ 2 ToUl, . 20 • t if Mr J. B. Hamilton, in a paper read before the Mining Institute of Scotland, gave the following mixtures for a daily feed : — No. 1. No. 2. No. 3. Beans or peas, 2 lbs. 2 lbs. • • • Maize (bruised), . 6 n 4 „ 4 lbs. Oats, . 4 „ 3 .. 8 ,. Bran, • i ■ ■ • • 2 „ 2 „ Hay (cut), . . 12 „ 12 „ 12 „ Stiaw (cut), . 2 .. 2 ., 2 n 26 „ 26 „ 28 „ No. 1 is a daily feed for a pony about fifteen hands high hardened to its work ; No. 2 for same size of pony new to work ; and No. 3 is for a pony doing no work. Mr Hunting * says that the quantity of food must be regulated by the amount of work required ; but about 100 lbs. of com, crushed and mixed with about 56 lbs. of chopped hay, will form an average week's provender for each horse. He considers that beans (or peas) and hay with either (1) oats and bran, (2) barley and bran, (3) oats and maize, (4) maize, will form equally good mixtures, and that we must be guided in our selection by current prices. Feeding is not, however, the only thing to which attention should be devoted. Keeping horses in good condition requires a plentiful supply of good clean drinking water, and they must also be properly bedded, and above all, kept well cleaned and groomed. It is too often left to the pony driver to attend to these matters, but no * Trans, N, Eng, Min, and Mech, E,, vol. zxxui. p. GI. H&OLAaS. 26S Ssf'" greater mistake can be made, especially if there are sufficient ponies to afTord work for an oatler, as manj pony drivers are mere boys, who have no experience whatever as to how a horse ought to be cleaned, and the majority of them are too careless to pay much attention to the needs of the horse or pony under their charge. Wherever there are more thau a dozen horees underground, it will, as a rule, pay to put _^^__^_^_^^^_ __^_ them under the chaise ^^^^■^^■^^^^^^MM^M^BM^H of a competent ostler or horse - keeper. Horses PMiwMgm should also have an opportunity of eating during working hours, as their work is ex- hausting, and a hoiae cannot retain sufficient food to maintain it for long intervals. Provision should therefore be made at the lyes or sidings, where the horsee stop, for them to obtain food while waiting. A visit- ing veterinary surgeon should also be appointed, where there are a large number of horses, to ' examine them periodi- cally, and to report upon their condition. Horaee underground ought to be properly shod at stated intervals. The cost of shoeing will on an average amount to about Cd. per week. The total cost of each horse per week may be estimated at 12a. to 15s., including shoeing, attendance, repairs to harness, feeding, and bedding. SteMe». — The arrangement of the stables b a very important matter, and it will pay to expend some thought und care in planning them. Many stables are merely formed in the workings, without any attempt at flooring or drainage, the result being that the floor gets worn into holes, making it very uncomfortable for the animals to rest on. Figs. 380, 261 show the construction of stables as sometimes TTTT Klus. 280, SSI. — llduandM 256 PRACTICAL COAL- MINING. adopted. The stalls, which are walled in on each side with a brick wall 14 in. thick, are 9 ft. x 6^ ft. x 6 ft. A gutter is formed down the centre of the lower half of the stall, and connected with a main gutter running at right angles to it, and in the direction of the road- way. A tram road is laid along between the rows of stalls, for convenience in cleaning them, and a passage is also constructed along the head of each stable for the distribution of food. The floor should be well laid with bricks, laid sideways, and carefully cemented in, the floor having a rise towards the head of about 2 in. in the yard. A large watering-trough should be placed outside the stables for the horses to drink, when going to and returning from work. Cost of Horse Havlage, — The cost of horse haulage depends on various conditions, such as the gradient of the road, the condition of the rails, roads, and tubs, especially the wheels, and whether the roads are wet or dry. The cost of horse haulage at the faces, i,e. lifting tubs from the faces to mechanical haulage, may be taken as 9d. to Is. 6d. per ton per mile ; the cost of horse haulage when used for conveying coal from lyes to the pit-bottom, in rakes or sets, may vary from 2d. to 6d., or sometimes as high as Is. per ton per mile. The cost for keep of horses, shoeing, harness, etc., has to be added. This may be taken at ^d. to |d. per ton per mile. Prof. William Galloway gives the following details of the cost of secondary haulage, t.c. collecting tubs from working places and conveying them to sidings : — System. Handputter, Horse, . Pony, . Hand, Agents. Boy, . Man and horse. Lad and pony, Man, . Uuit of Weight Day's Work Cost per Day. lbs. 550 2800 896 896 yard, tons. 1610 6864 6677 5252 s. d, 2 0 6 6 4 5^ 3 8 Cost per Ton per MUe. 5. d. 2 2-3 1 8 1 4-8 1 2-74 ! In these examples the gradient of the roads where the different agents are employed will vary considerably. Self-acting Inclines. — Self-acting inclines may be divided into three different classes: — (1) Balance braes or jig brows, where a balance weight is used. (2) Self-acting incline working with two tubs on the cut-chain principle. (3) Self-acting inclines working in the ordinary way with trains of tubs. In the great majority of mines, the conditions are such that very often one or all of the above sorts of incline can be employed. Where the inclination of the seam is sufficient to allow them to run freely, they form very easy and economical means of haulage. Balance Brae or Jig Brow, — This is the simplest form of self-acting HAULAOB. 257 incline, and is iisiiallj employed at the faces for bringing out a single tub at a time, to a siding or main incline. It ia worked by a rope or chain, more usually the former, passing round a wheel, 18 in. or 34 in. diameter, fixed between two iron jaws which terminate in a screwed bolt passed through a prop at the face, and held tight by a nut and washer (fig. 282). Two sets of rails are provided, one set having a narrow gauge for a loaded carriage or bogie to run on, and the other set with wide gauge for the tub to run on. The bogie is filled with scrap iron, and is generally so balanced that it can bring up the empty tub without requiring any brake on the wheel. The full tub on de- scending draws the loaded bogie up to the face, and tbe bogie on descending brings up the empty tub. To pre- vent the loaded carriage from running back, when the full 7 tub is disconnected from the _ „.„ ,. , . rope, at the toot of the in Fio. 282.- J« brow. r^nRement cline, the rope is held fast as (iti.o"a.r«oodth.m.fi»rii,..taciin«,.«»t shown in fig. 283. To the short piece of chain attached to the capping of the rope, an auxiliary piece is tiaed. To a double sleeper is fised a bolt over which a link To fiopt Fio. of the aiuiliary chain ia passed, and held in position by a pin. This holds the rope in position until the empty tub ia attached. Jigs are beat suited for seania where the gradient is ^eater than 1 in 6, and the author has seen them workii^ aatiafactorily in roads 17 258 PRACTICAL COAL-MINING. having an inclination of 35° to 40*", but in such cases great caution must be exercised, and the roads should be thoroughly well laid. In highly inclined roads the wheel at the face ought to be provided with a hand brake as shown in the sketch, and the prop well notched into the roof and floor. Unless this is carefully attended to, accidents are almost sure to occur. Cut-chain Incline. — This is a somewhat different form of self-acting incline to the above, for instead of a loaded carriage being used, a Branch Rosd Branch Road Fio. 284. — Enlarged plan of cut-chain, showinff main and branch roads, with lift rails out of i)osition. regular double road is required, and the weight of the full tub going down brings the empty tub up to the face. This system is largely used in Fifeshire and other districts of Scotland, and can be employed either in stoop and room or longwall working, if the inclination is sufficiently great. The working of this system will be understood from figs. 284-286. Metliod of Working the Cat-chain Incline, — Suppose a tub requires to be run down from A, the portion of the chain not required is detached and left lying on the road between the rails. The full tub is then attaclied, run down, and an empty one brought to A' ; another HAULAaB, 259 Th« rop« pMsat Toqnd t wheel at the top, W, Gf(. 28S, and haa connections or ' cuts at each of the ' hkbging on ' stsees, A B C D, at none ol which are »d; platfarms used, bnt the road is levelled out and two platei P P, fisa. 284, 2eS, with lift rails R B, inas over them t« the raiU on the opposite side. Fig, 286 shows a plan of how these branches ere arranged. FlOH. 285, 286. — Cut-chain inclinr. 260 PRACTICAL COAL-MINING. HmIl, Figs. 287, 288. full tub should be kept ready at A' to be run down and bring up an empty to A, so that the chain can be again connected and ready for a * cut * at any of the other branches B B', C C, D D'. At the parts where the chain is cut, special links are required for disconnecting and reconnecting the chain. These links are shown in figs. 287, 288. The thin part a of the link in fig. 288 is made so that it fits the Ihik in fig. 287 through the opening 6. When the two links are thus connected, it is impossible for them to be separated, as no other part of the link except the part a can pass through the opening h. At each branch road, highly inclined (30' to 45") from the horizontal, the roadway is levelled out and cast-iron plates laid down, with * lift ' R rails to pass over them to connect the rails above and below the branch. When a tub is being run down from a branch road, these 'lift' rails are lifted out of position and laid aside until the full tub is taken down and the empty one brought up, when they are again replaced, which leaves the road joined up ready for tubs to be run from any of the other branches above. If the gradient does not exceed 1 in 4 or 1 in 3, the lift rails are usually dispensed with, the floor of the road at the branches simply being levelled out somewhat, and the plates laid down with a gradient of 1 in 15 to 1 in 20, and the tubs allowed to run over them without the aid of the *lift* rails. To enable the tubs to pass easily over these plates, they are cast with a groove the gauge of the wheels, so that when the tub leaves the rails the flanges of the wheels enter these grooves, in which they run until the rails are again entered upon below the branch. When branch roads are worked from one side of the heading or incline, the arrangement for running the tubs is somewhat different.* A wheel is fitted up at the top of the heading in the way already described, and the chain passed round it, one end reaching the foot of the incline and the other lying near the top. At each branch road or * cut ' there is a disconnecting or cut-link in the chain as in the first arrangement, so that the upper portion can be disconnected as required. At the branch roads plates, with grooves in them, are laid down in the same same way as shown for the incline, with branches worked from both sides. At a short distance above these plates, about 6 ft. or so, a small grooved wheel is fixed, preferably between the two lines of rails. Whenever a tub requires to be run down from any of the branch roads the chain is disconnected at the cut- link, and the end of the lower portion passed round this small pulley and connected to the end of the load tub. To prevent the tub from running off" before the chain is attached, a block made of a piece of wood 4 or 5 inches square and of sufficient length to stretch across * Trans, Inst. Min, Eng., vol. xiv. p. 196. both rails, is fixed acrosB them. Thia block turns on a bolt at one end, and when in position is fixed bj an iron pin at the other end, which passes througli the block intu a plank or sleeper on tiio roadway. When the end of the cliain has been drawn round the wheel and Sied to the tub, the latter is run down to the foot of the incline, an empty tub being brought up on the other line of rails to the branch road. Like the arrangement previously described, two tubs should be run from each branch so as to bring the chain back to its original position ready for connecting. If this is not done, and only a single tub is run down, the position of the' chain reaching from the branch road, from where it has been ' cut,' will have to be lifted across to the centre of the line of rails where it was originally, and this can only be done if there are no centre props on the incline. On the wheel at the top, if the gradient requires it, a brake is fitted, operated from each of the branches or benches by means of a wire attached t« the brake - handle, and led down the whole length of the incline. A large amount of ooal can be run down these 262 PRACTICAL COAL-MINING. iuclines when they are properly constructed. They are beat suited for lengths of 50 to 100 fms., beyond which they do not work so well. The same system can also be used with a balance - weight in long-wall working where it is often difScult to keep the road wide enough for a double tram road. The cut-chain system can be worked on any inclination from 10° up to 45°. Sdf - acting Ineline with Traine of T^ft*.— This is the commonest form of incline, and can be used with great advant^e where the gradient is suitable. The most usual arrangement is to have a ^ rope passing two or three ■z times round a drum or ■-I wheel, to give sufficient ° friction and prevent slip. .| The dnim or wheel is fitted S with a good brake, and the g rope is attached to the full ■J, train of loaded tubs, which S by their own weight bring a J train of empties to the top f^ of the incline. The best plan is to have a double mad tliroiigliout (fig. 289), as the incline will work more satitifactorily than by using two or three seta of rails. If the roof is bad it may be difficult to make and maintain a road of suffi- cient width to admit of a double train line throughout. In such circumstances two or three rails may be used with a pass-by in the centre. Fig. 290 shows an incline with three rails and pass-by. Fius. 291, 292. -Endless ohain incline. If tl'e inclination is great the beat resulte are got by a drum instead ot a wheel for lowering the tubs, as it can be better HAULAGK. 263 kept under control ; on the other hand, the ropes are more difficult to keep in line with the roads, owing to the lapping of the ropes on the drum. If the inclination is not too great a suitable wheel gives very good results, and has the advantage of taking up little space, and the ropes can be kept in a straight line with each road, if the wheel is fixed horizontally. About 3* is the least inclination an incline will work at easily, but the length of incline is a determining factor, as the longer the incline the greater will be the weight of rope and the friction. On the other hand, the shorter the length of incline and the heavier the load, the better will it work. Self-acting inclines are sometimes worked on the endless rope or chain principle, with the tubs attached singly at stated distances apart. Where the conditions are suitable this plan yields very good and economical results. Figs. 291, 292 show the arrangement of such an incline worked with an endless chain, and fig. 293 illustrates the brake wheel used on this kind of incline, and which is somewhat differently arranged to an ordinary incline wheel, as the attendant has to handle the brake, and also to attach the tubs to the chain. The tube are attached to the rope at intervals of 20 to 30 yards ; where a tub has to be attached the Fio. 293. —Brake wheel, attendant applies the brake and brings the rope to a standstill ; the tub is attached, and the rope is allowed to move until the next interval. The advantages claimed for this system are : small cost for upkeep of rolling stock, the slow speed causing fewer breakages ; regularity of delivery ; and economical working. The length makes little difference, and there is a little less expenditure in making benches at the top and bottom of the incline. Although roads with regular gradients are best adapted for the application of this system, it can also be successfully employed upon roads the inclination of which varies. To find the gradient at which a self-acting incline will work, the following method can be employed : — Let W = weight of full train of tubs. w= ,, empty „ t^i = ,, rope or chain. F = friction of full train. /= ,, empty train. f,= ,, ropie, rollers, etc. I = tangent of angle of inclination. The weight of the full load must be able to overcome that of the empty load plus the friction of both loads, and of the rope, drums, rollers, and accessories ; 264 PRACTICAL COAL-MINING. that is, (W X I) F must be greater than (W x I) +/, and (W - vj) 1 greater than F +/! From this reasoning we can establish the formula — * (W-t^-u;i)xI-(F+/+/J .M = Jjt/-t/i . The angle of inclination thus obtained would be that at which the pull of the full train would exactly balance the resistances on the incline, so that it would require a greater angle of inclination to enable the system to work easily. Example.— Find the angle of inclination for a self-acting incline to act pro})erly if the trains consist of 10 tubs, the gross load of each full tub being 16 cwts. and each empty tub weighing 5 cwts. The weight of the rope is to be taken at 5 lbs. per fathom, the length of the incline 150 fms., and the weight of drums at 8 cwts. The friction of the tubs may be taken at f^, and that of the rope and drums at ^. /10xl6xll2\ /10x5xll2\ (8x 112) + (160x5) Then I = V 70 ri 70 F 20 (10x16x112) - (10x5x112) -(8 x 112) + (160x5) 266 + 80 + 82-3 418*3 1 ,,. „r- = _ ■*. ■■ — ) or 1 in Zo o. 17,920-6600-1646 10,674 26-5 To make the incline work easily, it should be 20 per cent, steeper, e.g,, 1 in 20. Carriage Inclines, — When the inclination exceeds 45' a carriage is employed to enable the tubs to assume a horizontal position. Fig. 294 shows the construction of such a carriage, which may be made to hold two, four, or six tubs. These carriages are much used on the Continent, where the measures are greatly inclined. Thej are also used in England and in the oil-shale and coal-mines of the Lothians in Scotland. On the Continent such inclines are often worked with a balance weight with a single road, so arranged that the balance weight passes under the carriage at the point of meeting. Blocks. — At the top of all inclines means must be adopted to prevent the loaded tubs from running prematurely down the incline. This is usually accomplished by means of blocks or stops. A common form of stop used is simply two blocks of wood working on pivots, one of which crosses the rail for the tub wheel to rest against, and abuts on the other, which is placed at right angles to it. * Staple ' or * Blind ' Pits, — It often happens that the coal is lowered from one scam to another by means of * blind ' or * staple ' pits instead of by an incline. These pits are not so expensive to make as an incline, and if properly fitted and the depth is not great a large quantity of coal can be lowered by their means. The arrangements at the top of these pits are shown in figs. 295, 296. The pits are usually fitted with two cages like an ordinary winding shaft, the cage with the full tub being able to outbalance and raise the cage with the empty tub. Sometimes one cage only is used along with a balance weight, but this is not such a good arrangement. In work- ing, these pits ought to be carefully fenced to prevent tubs from * It must be remembered that in the above formula I does not represent the angle of inclination, but the tangent of that angle. The former can be found from the latter by consulting trigonometrical tables. being pushed into them when the cage ia not in position. Many accidents have taken place through lack o[ this precaution. Fio. 294.~CikrriHge fur tub on iaclines. Haulage by Stationary Engines.— We now come to the different systems of haulage by stationary engines, which play uuch important parts in the successful working of modem collieries. These systems can be divided into — The workings of a colliery may be so distributed that two or more of the above systems of haulage can be applied in different sections or localities. Direci Rope Haulage. — When the inclination is sufficiently great for the train of tubs to run down of their own accord, and to over- come the friction of the rope to which they are attached, and of tubs, drum, etc,, a single rope may be used with advantage. An engine with a single drum is employed, the latter being so arranged that it 266 PRACTICAL COAL-MINING. caii be thrown out of gear and run looeo on the ahaft. The engine draws the full train of tubs against the inclination to the pit-bottom, while the cmptj train runs in-bye and dragB the rope after it, the drum being out of gear and running loose on the engine shaft. To work this aystem Buccesafully the inclination should be not less than 1 in 36. For single rope haulage the engine is best placed at Arraugement ot brake wlieel tor BUpln pit. the pit-bottom, as this gives the engtnouian the advantage of having everything in view, and mistakes are uot so apt to be made by taking the tubs too far when the train is approaching the bottom. The main advantage of this system is that it is cheap, so far aa first cost is concerned, a single road and one rope only being required, while any number of branches can be easily worked by the same engine. Main anil Tail Rirpe Haulaije, — When the inclination is insufGcient or irr^ular, and the empty train unable to run in-bye by it« own Fir. 297. — Main and tail rope lualage. weight, it is necessary to use another rope called a ' tail ' rope to draw in the empty tuba. The tail rope is wound on a dnim on the same shaft as the main rope dnim, and passes along the side or roof of the roadway, till it reaches the far end of the road, where it passes round a wheel c placed either vertically or horizontally (fig. 297), and cornea on to the main roadway, where it is attached to the end HAULAGE. 267 of the full train of tubs, the main rope being attached to the front of the latter. The tail rope, therefore, requires to be twice the length of the road. Working of System, — Suppose an empty train of tubs to be stand- ing at the pit-bottom ready to be hauled in to the workings, the drum with main rope will be thrown out of gear, and allowed to run loose on the driving shaft, while that on which the tail rope is wound will be in gear. The engine will haul the empty train in-bye with the tail rope attached to the front of it and the main rope attached to the back. When the loaded train has to be hauled out-bye these conditions will be reversed, the tail rope drum will be thrown out of gear and the main rope thrown in gear, the tail rope being now attached to the back of the train and the main rope to the front. The tail rope is usually a good deal lighter than the main rope, as it is only required to haul in the empty tubs. It will be seen from the above that this system of haulage requires a length of rope three times the length of road, the tail rope requiring to be twice the length and the main rope c<|ual to it, so that when both ropes are connected to the train of tubs it practically becomes an endless rope working on a single road. Guiding the Ropes. — As only a single road is used, the tail rope is guided either along the side of the road or along the roof ; whichever F108. 298, 299.— Guides. method is adopted the pulleys ought to be set so as to run freely, otherwise there is great wear and tear on the ropes. When the tail rope is guided overhead, the pulleys are often fixed as shown in figs. 298, 299. A pulley or roller is hung by means of two hangers, about 6 in. X 3 in. x | in. tapering to | in. diameter at the top, where it is fixed to a bearer by means of a nut and washer. For guiding the rope along the side of the road the arrangement of pulley shown in fig. 300 may be adopted. If there are curves on the road, swing- ing pulleys (fig. 301) should be used, which will enable the rope to take the line best suited to it. Fig. 302 shows the general arrange- ment of road with pulleys for main and tail ropes. Detaching the Rope, — When the train of tubs is near the shaft the rope is detached, and the hauling engine brought to a standstill. The rope may be disconnected either by hand or automatically. When this is done by hand a common shackle may be used (fig. 303), 268 PRACTICAL COALMINING. the couiiecting bolt having au eyo for a Boiall pin to pass through prevent it from working out. More frequently an automatic 'knock-olT' ia uaed, as shown in f PiQS. 300, 301.— Guid«8. 304. Other 'knock-off' arrangements are illustrated in figs. 305, 306. A somewhat dlifcreiit arrangement for antomaticatly detaching the rope in shown iti figs. 307, 308. This apparatus, which is often Fia. 803.— Shkckle. termed a ' monkey,' is placed on the front of the train of tubs, and consists of a crank a, working on a standard /', which is fixed to the tub by a fork arrangement, or special clamp fitted to the tub. To Fid. 301.— Automstic knock-ofT the end of the crank it the rope. At the pit I c, with a pin at the end for fixing e it is desired t Fio. 816. — Working branches. pass round the bend they again attach themselves automatically to the chain. Method of attaching Tubs to Chaim, — This is usually done by fixing to one end of the tub an iron fork, into which the chain drops. When wood tubs are employed, a fork is used, being fixed by means of two nuts and bolts. With iron tubs the grip is a part of the tub itself, and requires no fixing. Sometimes movable grips are used to adjust the height of the chains according to the quantity of coal loaded above the level of the sides of the tubs. The chief advantages of the endless chain system are the slow speed HAULAGE. 275 at which it travels, and the small amount of wear and tear in rolling stock entailed, besides the small cost of upkeep of roadway. The principal disadvantage is the heavy weight of chain to be driven where the haulage is long. This system is better suited for surface haulage than for under- ground working, many such arrangements being at work for convey- ing coal or other material long distances, as when a colliery is so situated that it would be impossible or inconvenient to connect it with the railway by means of a branch line. Endless Boife. — This system, as its name signifies, consists of an end- less rope travelling in a double roadway, and to which the tubs may be attached either singly at intervals along the rope or in trains. The engine for driving the rope is almost invariably placed on the surface. Fig. 317. — System of working curves. and the power either conveyed direct or by a * band ' rope reaching to the pit-bottom, where it drives a main shaft from which the power is derived for other endless ropes. The general arrangement in end- less rope haulage (fig. 318) is as follows : — At the mouth of the shaft are two pulleys for carrying the rope from the driving wheel into the shaft. At the pit-bottom are two other pulleys, placed vertically to receive the ropes, and immediately below these are two other pulleys, placed horizontally to enable the rope to make a right angle with the shaft, and pass into the workings to the in-bye end, where it passes round a loaded wheel d or an ordinary pulley placed horizontally. In another arrangement the loaded wheel or tightening carriage is placed on the empty rope side near the pit-bottom. This is un- doubtedly the best position. Arrangement of Engine. — For endless rope haulage, where a large quantity of coal has to be drawn, it is best to employ a double cylinder 276 PBACnCAL COAL-MINING. engine well geared down. With a modem haulage plant for endless rope, the two cylinders arc placed horizontally, and the piston rods connected to disc cranks fitted on to the main driving shaft. On this shaft are two small geared wheels, working into two latter toothed wheels, which are keyed on to a separate shaft, on which is also fixed the driving pulley or pidleys, the number of which varies with the number of ropes to be driven. These pulleys are now usually arranged with clutch gear so that they inay he rapidly arrested without bringing the engine to a standstill. As to whether the power should be conveyed through g a band rope or not, there are differences 1 of opinion. Where more than one I" endless rope is required to work diller- t ent sections, the tw^nd rope method is f to be preferred. If four different ^ sections are worked by endless rope, a and each separate rope is worked direct $ from the surface, this would necessitate e four double lengths of rope being g conveyed down the shaft, which, owing =5 to the complications that might arise w in the event of any of the ropes break- [ ing or getting entangled with each 2 other, woidd he altogether nudcsirablc. ^ On the other hand, when a l>and rope bI; is used only a double length of rope requires to be led down the shaft. It must not he forgotten, however, that as the whole of the power must be con- veyed through the band rope, this would require to be a good deal heavier, and therefore more expensive than the hanlage ropes worked from it, while there would also Iw tlie increased ex- penditure for the clutch arrangement at the pit-lx>ttoni. With the band rope system, any number of ropes can he worked, according to the power available. They are under the direct control of the attcndnntH at the shaft l>ottom, who can stop any of them without signalling to the surface, which is a great advantage, as one section may not have sufficient coal to keep the eudlesa rope HAULAGE. 277 constantly at work, aiid such rope can therefore bo throwu out of gear, while the other sections go on hs usual. For a very deep shaft the coat of the band rope becomes, on the other hand, a serious iteui, although even then it would be less expen- sive than taking all the ropes up tu the surface. Everything con- sidered, the band rope system of conveying the necessary power is much to be preferred. Driving Pulleys.— The rope is usually actuated by a clip pulley. There is a considerable number of different types of pulley in use. The Barraclough pulley is a well-known device for endless rope haulage. Round the periphery of the wheel and opposite to each Other are fixed a number of short taper clips fitted to receive two aliding jaws a a (fig. 319), upon which the rope works. These jaws c 41/ Fius. 319, 320.— Barracbugh'B pulley. rest on springs 6, so that when the rope comes on to them, the weight forces them down on the springs, and narrows the opening between them, thus giving the necessary grip to the rope. At the point where the rope leaves the pulley the springs give assistance in releasing it. Another pulley, much used in Scotland, is shown in fig. 320. The rim consists of two segments e, and d, bolted together. Between these segment* is placed a layer of wood e on which the rope works. The opening on the rim of the pulley being y-shaped, the rope obtains the necessary grip by wedging itaelt at the bottom of the opening. Owing to the low coefficient of friction between iron and iron, and also to the wear of the rope in \inlined pulleys, it has become customary to pad them with softer material than iron, to increase the gripping power and so increase the life of the rope. Segments of hara wood are used, but require fre<^nent renewal, and soon lose their gripping power. Segments of india-rubber have been tried with good 278 FBACnCAL COAL-HINING. efiecte, and last a considerable time. PoeuJblj the beat substance for this purpoee is well-Beaeoned leather driven into the rim of the wheel in segments aa (fig. 321), and turned true. This is said to give a good gripping surface that will laat from two to three years. When a large amount of power requireti to be transmitted, groored pulleys and counter-pulleys or lacing wheels are sometimes used to impart the necesaaiy friction to the rope. Both pulleys have from four to six grooves in the rim, the driviug wheel a having one more than the guide or counter-pulley b, which is set immediately in line with the other (figs. 322, 323). Taking up Slatk Rope. — No matter how perfect the driving pulley on the surface may be, some arrangement for taking up slackness will require to be adopted. The usual plan is to have the rope passing round a tightening pulley. There are various ways of arranging this pulley. Sometimes it is fixed as shown in fig. 324, and fitted with a long screw and nut, which can be adjusted as required. But this system of tightening is not at all to be recommended. What is required is some arrangement that will automatically adapt itaelt to the varying load and wear of the rope. To accomplish this, a wheel is usually mounted on a tension carriage to which is attached, by means of a chain passing over a pulley, a weight (see fig. 325) workiog in a small pit below the level of the road. Sometimes the tension-carriage is attached to a loaded tub, working on an inclined plane. The HAULAOB. 279 weight required can easily be found when the rope is set to work. The tension pulley is usually placed as near the pit-bottom as ^ possible, although it may also be placed at the further end of the road. It is, however, often very inconvenient to have it in the latter position. Speed of Rope. — With endless rope haulage, the speed at which the rope travels may vary from 1^ to four or five miles per hour, but the best results are obtained when the rope is travelling at a speed of from two to three mUes per hour. Working of System, — The system can be applied either : (1) with the rope travelling over the tubs ; or (2) with the rope moving beneath them. The tubs are also attached to the rope in two different ways: (a) singly at specified distances apart, by means of ' clips ' or ' jiggers '; (h) in sets or trains by means of a ' clip-bogie ' and gripper. The first method is undoubtedly the better of the two, as by this system the supply of coal at the pit-bottom is regular, and the load on the engine more evenly distributed, whUe no attend- ants are required except at each end of the road or at branches. Some, however, prefer the 'clip-bogie system,' as being safer, and better adapted for working a number of branch roads. It is somewhat more expensive than the first-named method. With either system a double road is generally employed, al- though sometimes a single road is used with pass-byes at intervals. When such is the case, the tubs are run in trains. It is often urged as a defect of the endless rope system, that it requires a double road, the construction of which is often difficult and expensive, especially where there is a bad roof. But a double road is not at all essential for the suc- cessful working of an endless rope system of haulage. At the Palace C!olliery and Bent Colliery, Hamilton, systems of endless rope haulage have been successfully at work for years, in I 5 -8 I CI e 280 PRACTICAL COAL-MINING. both cases arranged on the nngle road principle. In the first the rope passeu under the tubs, while in the second it is overhead, the Utter being probablj the more successful method. At a short distance from the shaft are set two parallel single roads, from different sides of the pit-bottom. These tvo roads are carried for the required distance, and are connected b; a cross drift into which the rope passes bj means of tvro wheels. These two parallel roads may be as wide apart ae required. The empty rope and empty tubs leave the pit-bottom at one side, while the full rope and loaded tubs arrive on the opposite side. This system has a great advantt^ over that where the empty and loaded tubs alike require FiQ. 32B.—Ti)iisiuQ carriage. to be handled at the same aide of the shaft. The rope can be easily extended into the workings. At the Bent Colliery much the same system was adopted, but the two roads, instead of being driven parallel, were taken along a more circuitous route, practically bo follow the faces, which enabled the tulis to be brought on to the rope with very little secondary haulage. The empty tubs can be taken ofT, and full tubs attached at any desired ])Hrt of the road, and if the empty tub is not required, or is not taken off the rope in the workings, it will return again to the pit-bottom on the side opposite that from which it left. Vlipt or Jiggers. — When the tuba arc attached singly to the rope, a clip or jigger is used. A great many different sorts of clipa are in use in dift'erent districts, each having i(« own special merits. A clip used in tjcotland a good deal for under-rope haulage is shown in figs. 326, 327. It consists of a pair of jaws . 120. HAULAOK. 287 between the rails. It also asaiste the tub to keep the rails while being attached to the rope, at the time of leaving the level landings. The clip used is shown in figs. 344, 345. The jaws are made to a radius of 3^ ft,, so that when the screw is tightened the clip has a firm grip of the rope in at least three places, at each end and in (o FiQS, 842, a*3.— B«T8l pnUeys, the centre. Ordinary clips were found to be of no use in this case, and hence the adoption of this special type. The full tubs are attached singly, and the empty ones sent down in pairs ; both the attaching and detaching being accomplished at all points without stopping or interfering with the speed of the rope. Fioa. S41, 346.— Eadleta rope clip used at Moston Colliery. There are several intermediate landings at which the full tubs are attached and the empty ones detached. Fig. 346 shows the method of working these landings. Sufficient roof is taken down to allow one full or empty tub to stand on the fixed lauding A B. There is a movable hinged landing A C, controlled by a balance weight in such a position that when it is lowered the empty tuba will run 288 PRACTICAL COAL-MINING. on to this platform instead of going further down the incline. When the tubs have arrived the clip is unfastened, and they are run on to the fixed landing AB, the movable landing AC being immediately pulled up by the balance weight into the position shown in the figure until it is required again. When a full tub is about to be clipped on to the rope, the movable landing A C is lowered, and the tub brought on to it, and without stopping the rope it is clipped and the tub started up the incline. Two boys are stationed at each of these stations to attend to the tiibs. The distance between the landings varies from 100 to 140 yards. The power MminRooe \\ Main Strap Ropt )j from surface Fio. 346. —Method of working landings at Moston Colliery. to work this and other ropes is derived from an engine at the surface, being transmitted by means of a band-rope working to a central station underground, the driving engine being compound, with cylinders 15 and 25 in. respectively, and having a stroke of 4 ft. All the pulleys underground are inclined (fig. 347) on the rope surface to the extent of 1-^ in. in 6 in., so as to cause the 2| turns of the rope (which are necessary to give the required grip) to be constantly slipping in the direction of the lesser diameter. Attached to the pulley working the incline is an ingenious brake arrangement. The brake-rim of the pulley is cast and faced with steel segments. Upon this surface four steel slipper-blocks a a (fig. 348) rest, attached to the framework by means of togglo joints bb, each pivoted on to a plummer block cc These ahpper-blocks are not set at right angles to the brake-rim, but at such an angle that, upon the wheel continuing to turn in the proper direction (shown by the arrow), the blocks are pushed off the rim ; but upon the incline rope being thrown out of gear, the screws b b tend to take a position at right angles to the brake- rim, and in so domg wedge the blocks firmly against the rim, and prevent the wheel from turning the opposite way. The rope is thus prevented from a backwaid movement. To further increase the braking power of the slipper-blocks, they are also attached to the frame by light spiral springs. When the pulley is thrown out of gear, its fiiat tendency is to revolve in a contrary direction, owing Fio, SIS. — Bnkeamnfjenietit. to the weight of tubs and rope on the incline, but this movement is immediately arrested by the automatic blocks coming into action. The incline for this haulage was laid with a double road through- out, with steel rails weighing Hi lbs. per yard, and fish-plate joints. The amount of coal drawn per shift of nine hours was 300 tons, which ia excellent work on a road of this description, OoBt of Haulage.— The cost of haulage is usually sUted in pence per ton per mile hauled, and will vary a great deal under different conditions, such as the inclination of the road, the number of 19 tl II II II II II II 290 PRACTICAL COAL-mNING. branches to be worked, and whether the rope can be kept continually at work during the shift or not. The following may be taken as average costs : — Manual haulage Is. 6d. to 88. per ton per mile. Horse ,, Sd. to 6d. Self-acting incline haulage 2d. to 3d. Single roue haulage 2d. to 6d. Main and tail rope haulage Ifd. to 21d. Endless rope (clip) ,, Id. to 2d. „ (bogie) ,, 2d. to 8d. Endless chain haulage id. to l^d. There can be no doubt that, with a well laid out haulage plant and under suitable conditions, the endless rope system is preferable in most cases. Even in steep roads it will compare favourably with other systems of haulage. In fact, the author is of opinion that the endless-rope system is the most suitable for underground work, whether the roads are flat or steep, and can be successfully worked if the roadways are properly laid out for such haulage. In two instances,* with single rope and endless rope systems, one of the roads dipping I in 3 and the other I in 4, and each being about 1200 yards long, and yielding an output of 800 tons per day, the cost per ton in the former was 5d. and in the latter Id. per ton. The cost of ropes by the endless system was 0*37d. per ton, which could not be any lower in any other system; for although a double length of rope was required, the difference in cost is always compensated by the reduced wear and tear. There will not, naturally, be the same disparity of cost in all cases, but, as a general rule, endless rope systems will be found to be cheapest. Advantages of Endless Rope Haulage. — While the endless rope system has the disadvantage of requiring double roads, it has many advantages to compensate for this. Amongst others are — The small number of attendants required for a given daily output. The slow speed, which prevents any loss on the journey, reduces to a minimum the risk of breakages, and thereby obviates the mischief con- sequent on such accidents, such as those which may occur when a train of tubs is trayelling at a high rate of speed in the main and tail rope system. The wear and tear on machinery, tubs, ropes, etc. , is a great deal less than with other systems of haulage. By attaching the tubs at equtu distances upart, the weight of the rope is carried along with less friction on the ground and pulleys. A regular and continuous supply of tubs is brought to the pit-bottom. In a road with vaiying degrees of inclination, the whole load is distributed over the whole lenffth of the rope, which is a great advantage. The empty tubs going m-bye also assist the engine to haul the mil tubs out-bye. Ropes last longer (on an average three to four years), while with main and tail rope the average is probably not more than one to one and a half years. • Trans, L M, &, vol. x. p. 497. HAULAOB. 291 Haulage Problems. Question, — A train of ten tubs is ascending an incline of 4^ in. rise per yard, each tub weighing with coal one ton. What power would be required, and what would the strain on the rope be ? 4i in. per yd. =1^=1 in. in 8. 4*6 Weight of train =r 22400 lbs. Friction taken at ^^ of the load -??^i??ii-^ = 320 lbs. Then ^Hi^iil-2800, the force required estimated in lbs., and 8 2800 + 820=8120 lbs. =the total strain on rope. Question. — Find the tension on a haulage rope with a load of 20 tons on an incline of 1 in 6. Let W=Ioad in lbs., H= vertical factor of rise, and L= horizontal factor of rise. WxH. Then tension = L Tension = ^^ ^ ^^^ ^ ^ = 7466 6 lbs., due to gravity alone ; 6 or allowing ^ for friction. Total tension = /^O x 2240 x 1 \ ^ ^^^^ .^ ^ g^^^^ ^ j^ Question. —Wh&t engine power, expressed in foot-pounds per minute, is required to draw a load of eight tons up an incline of 1 in 5, at a speed of five miles per hour, excluding friction 1 Speed of rope = ^^^^^ = 440 feet per minute. Load ^8 X 2240x1 ^3^3^ ^^^ 5 Engine power required (load in lbs. x speed in feet per minute) =8684 x 440= 1,676,960 ft. lbs. per minute. Question. — What size of engine, length of stroke, etc., would be required to haul 400 tons per shift of nine hours, from a road 1000 yards long and dipping 1 in 12? The system of haulage to be main and tail rope, and the speed of rope six miles per hour, the diameter of the drum being 6 ft. Speed of rope per minute=^i^^?? =628 ft Time per trip = ^^^^^"^ "" ^ = 1 1 minutes. Time allowance for changing at each end, about 4 minutes. Total time per trip, 11 + 4=16 minutes. Load per trip= ^ =11 tons (approximately). 292 PRACnCMi COAIi-MINING. Suppose the tubs hold 10 cwts. each, and to weigh 4 cwts. each when empty, twenty-two tubs will be required each trip, and the weight of the tubs will be 22 x 4 = 88 cwts. or 4*4 tons ; therefore the gross load per trip will be 11 +4'4, or 15'4 tons. 15'4 X 1 The load due to inclination = — — — = 1 '28 tons. /l*28 X 8 The oircumfeienoe, C, of the rope required would be = ^ — =| — - = 1 '84 Weight of rope per fathom = C x '9 = 3 '06 lbs. Total weight of rone = 600 x 2 x 3 -06 = 8060 lbs. Taking friction of load equal to 32 lbs. per ton, and friction of rope equal to ^th its weight ; then Friction of full load =15*4 x 32 = 492*8 lbs. And friction of rope = ???? =163-0 lbs. *^ 20 Total friction is 492*8 + 163 = 646 '8 lbs. Total load = full load + rope + friction = 38201 -8 lbs. Total resistance to engine =(i^^iii^?i?l±?^ + 64 6 '8 = 3620-4 lbs. Now the work done in the engine is equal to the work done on the plane, and can be expressed by the formula : D^ X 7864 xPxLxNxM= load in lbs. x circumference of drum in feet Assume the effective steam pressure to be 45 lbs. per sq. in., and the modulus M, f for single engine and f for coupled engines, the length of stroke being 3| ft. .-. Dax7854x46x3-5x2xt = 3620-4 x6x 3*1416 After cancelling D'^ x 16 x 3 *6 x -8 = 8620 4x4 16 X '2 . D_^/1061-8=i8-8in.. "" V— 3^6 the size of engines required. This problem may also be worked out by the formula : D»x 7864 X PxLx N x M=(Wx A) + (friction xcir. of drum in ft.), or D=V^' (W X ^) + (F X cir. of drum), •7854 xPxLxNxM where as before, D= diameter of cylinder in in. L= length of stroke in ft. M = efficiency of engine. P=efrectiye steam pressure in lbs. per sq. in. N = number of strokes per revolution of the drum. W= weight of loaded train in lbs. F= friction of loaded train in lbs. and rope. A = vertical height which the train is raised during one revolution of the drum. A8A = «-^-l:llliiil = l-57ft HAULA6B. 293 Taking the same figures as before, we have, D^^(l-5'4x2240xl'67)-h(645Tx6x8a416_ .3-3:^7^3^18^ ^ 7864x45x3-6x2xf ^ Question, — Find diameter of cylinder required, length of stroke, etc., to haul 300 tons per eight hour shift from a road dipping 1 in 20, laid with tram rails. Length of road 600 fms. Tubs to weigh 4 cwts. and hold 10 cwts. Size of driving wheel 6 ft. diameter. System, endless rope with a speed of two miles per hour. Tons per hoar= — =37*5 : speed of rope 8520 yds. per hour. 8 Tubs per hoar=87'5x2 = 75: distance tubs will have to be apart on rope = — -46-9 or 47 yds. (for simplicity). 75 600 X 2 Number of tubs on rope at once= — — — =25*55, approximately 26, ue, 26 full and 26 empty. Weight of loaded tubs, = 26 x 14 x 112 = 40768 lbs. „ empty „ = 26 x 4x112=11648 „ Weight of rope, say at 4 lbs. per fathom = 600 x 2x 4= 4800 ,, ToUl=57216 „ Suppose the total friction is A th . '. -' ^^ - V^ 1 907 '2 lbs. ,,,,.,.,. full load 40768x1 =2038-4 lbs. Load due to uiclination = . — ^ — n — " — sv^ — inclination 20 Total load to be overcome by engine = 2038*4 + 1907*2 = 3945*6 lbs. And as before, work done by enghie = work done on plane during one revolution of drum. Assume effective steam pressure at 50 lbs. per sq. in., and the number of strokes per revolution of drum at four. . *. D^ X 7854 x50xLx4x| = 3945-6 x 6 x 3 '1416 After cancelling D^ x L, - ^^^^'^""^ = 591 9 ^ 50 X '4 V5gi •Q —— =14-00 in. The size of engines required would be therefore 14*00 in. diameter, with a 3 ft. stroke geared two to one. This problem may also be worked out by the formula D- /(F X cir. of drum) + ( W - w)^ ^ •7854xPxLxNxM * the letters having the same value as in preceding question, and in this case to = weight of empty tubs. HereA-20ft. : 18*84 ft. : : 1 18*84x1 20 = •94 ft. .., D^ y/{"i907 -2x6x3-1416} + {57216-(n648 + 4800)}-94==A/7^272-64_^^.QQj^ ^ •7864x60x8x4x1 ^ 376*9 CHAPTEE XII. PUMPING. In all mines water is met with in greater or less abundance, shallow mines being, as a rule, more heavily watered than deep mines, owing to more frequent occurrence and greater width of the cracks or fissures in the overlying strata by which water can reach the workings, and to the absence therefrom of impermeable beds. In deep mines, which are seldom troubled with much water, such firm impermeable beds of strata are always present to some extent in the overlying strata, and prevent the water from entering the workings. The different methods of draining mines of water are by means of adit levels, tanks or chests, siphons and piunps. Adit levels can only be utilised under certain conditions, such as when the mine is situated on the side of a hill, or where the work- ings are at a higher level than some parts of the surrounding country. These conditions rarely exist in connection with coal-mining, unless in the opening out of virgin coal-fields in hilly countries. In metal- liferous mining, adits are, however, much used, many of them being of great length and costing large sums of money. In the Freiberg district of Saxony there is an adit level 8^ miles long, or, including branches, 25 miles in length, which cost about £360,000, the length of time occupied in this important work having been thirty-three years. ''^ The Halkyn adit in Flintshire is about four miles in length, and drains a large area to a depth of 230 yds. It is estimated that this adit is now discharging 1 5 million gallons per twenty-four hours, or a total weight of 66,000 tons, the whole of this water being a natural flow. Tariks or Chests. — If the quantity of water is not great and the pit is deep, it would be expensive to lay down a special pumping plant, while the water may be raised by water tanks or chests, especially if the winding engines are not fully employed drawing coal. The quantity of water dealt with in this way should not exceed 30 to 40 gallons per minute throughout the twenty-four * Ore and Stone Mining ^ Sir G. Le Neve Foster, sixth edition, p. 462. PUMPING. 295 hours, and this should be regarded as the maximum which should not be exceeded. Where there is a considerable quantity of water to be dealt with, pumping will be found the cheapest method. In drawing water in tanks great injury is often done to the winding ropes, through part of the water falling back into the shaft and washing the grease or lubricating oil off them, and also by the great strain they have to undergo in lifting heavy tanks full of water. The load is often very much heavier than the usual load of coal. The dipping of the tank into the water causes ^ slack,' while the vibration of the rope causes repeated bending to occur just above the capping, which tends to injure the rope, and if not carefully watched may result in breakage. Siphons, — The siphon is not applicable in the same way that a pump is, since by the former, water must always be delivered at a lotoer level than that of the receiving end of the pipes. We may, therefore, define a siphon as being an apparatus for conveying a liquid from a higher to a lower level over an intervening height. In construction the siphon is a simple piece of apparatus, and consists of a U-shaped pipe, one limb of which is longer than the other. The short limb dips into the liquid to be siphoned, and the other discharges it at a lower level. A vacuiun being continually formed by the escape of water from the longer limb, the pressure of the atmosphere, acting on the free surface of the water into which the shorter limb dips, forces it up the latter, when, having reached the highest point of the column, it descends by gravity with a velocity proportionate to the difference of level between the outlet and the free surface of the source of supply. Since the action of the siphon depends on the atmospheric pressure it is obvious the height to which the water can rise will never be greater than that of the water barometer at the time, which at greatest is about 33f ft., no matter what the amount of fall may be at the discharge end. lu practice the height to which the water will rise will not be more than 26 or 27 feet, the difference being due to the friction of the wat«r in the pipes, but it will be better if the vertical height does not exceed 20 or 22 feet. To start the flow of water in the siphon, the two ends must be closed by plugs or taps. Water is then poured in at the highest point until the pipes are filled ; this opening is then closed and the receiving and discharge ends are opened. The water in the pipe discharging produces a vacuum, thereby setting up a continuous flow. A better and more economical arrangement is to place a small hand-pump on the siphon at the highest point of the pipes, to pump the air out, and thus allow the water to rise. The air and gases held in water are liberated on moderate reduc- tion in pressure with great ease ; and as nearly all water contains more or less dissolved gas, this will be liberated in the siphon at its highest point, and may accumulate there until the pressure equals 296 PRACTICAL COAL-MINING. that due to the acceleration head, when the siphon will cease to flow. In laying down a siphon the greatest care should be exercised, so that it will have an opportunity of working under the most favour- able conditions. The pipes should be laid with a regular gradient all the way to the highest point, and the pipes should be of sufficient diameter for the water to flow with a velocity that may reduce the friction to a minimum. The joints should be thoroughly air-tight ; if the siphon has to continue working for any length of time, the joints ought to be run with lead, as this will be the most satisfactory and cheapest way in the end. A ' tail clack ' should be put on at the bottom of the receiving end to prevent the pipes from getting empty when the siphon stops running. rmnpe. — The best and most usual method for raising water from mines is by pumping. The first point of importance is the capacity of the plant required. In deciding this it is necessary to ascertain, as nearly as possible, the maximum quantity of water likely to be met with both in the shaft and in the workings. In sinking a shaft in a new and untried district it is impossible to do so, but in districts which have been well opened out it can often be done without much difficulty. The plant should be capable of raising a larger quantity of water than any ascertained maximum, so that a sudden inflow could be dealt with, if necessary, to prevent the flooding of the workings. Pumps for raising water in mines are generally of the recip- rocating type and may be classified as : (1) Plimger or ram pumps ; (2) piston pumps; and (3) bucket or lift pumps. Other kinds of pumps are also employed, such as the centrifugal and Fontigaine pumps, but these can only be adopted for limited lifts. The power employed is either (a) steam, (h) compressed air, (c) water or hydraulic pressure, (d) electricity. Conditions affecting the Working of Pumps, — The working of piunps is influenced by various conditions, such as : (1) The height at which they are placed above sea level, i,e, atmospheric pressure conditions. (2) The temperature of the water. (3) The size and length of delivery and suction pipes. (4) The area, weight, and lift of valves. These conditions have all to be carefully considered in designing or deciding upon the necessary pumping plant for a given position either on the surface or underground. The chief requirements mining pumps are expected to fulfil are : (a) They should be capable of working for long periods with little repair, packing, or adjustment. (b) They should be capable of being operated mider water (a particu- larly desirable feature in sinking pumps), (c) They should be capable of passing sandy or dirty water, and sometimes acid water, without too rapid deterioration or corrosion, (d) Their speed and capacity should be easily adjustable to suit the varying inflow of water. PUMPING. 297 Pump Fittings, Pipes, — The pipes used in connection with pumps may be made of wood, cast iron, or wrought iron or steel. Wood pipes are seldom if ever used in Britain for pumping, but in some parts of the United States, and where the climate is extremely variable, they are much used for certain descriptions of work, when the pressures are light. For pressures not exceeding 85 to 90 lbs. per sq. in., or a head of water equal to about 200 ft., they are said to be economical. The advantages claimed for them are that they con- tract and expand to only a small extent, and are therefore well suited for climatic changes, while they offer little resistance to the flow of water, and do not decay readily if water is kept constantly flowing through them. They are built up with staves, much like ordinary barrels, and are strongly bound with wrought-iron hoops. CSast-iron pipes were formerly almost exclusively used for pumping, and are so still to a very large extent, but for certain classes of work steel or wrought-iron pipes are displacing them. The great dis- advantage of cast-iron pipes is, that where they have to be of a large section, they are very heavy and difficult to handle. The joints in this class of pipe are usually made with a conmion flat flange, and an india-rubber ring inserted between them, the joint being well secured by nuts and bolts. For deep lifts and heavy pressures the top flange should have a groove cut in it, while on the bottom flange a rib should be cast to fit into this groove. An india-rubber joint of circular section is fitted into the groove and the rib on the other pipe fitted on it, the two ends being well screwed down with nuts and bolts in the usual way. Wrought-iron and Steel Pipes, — Pipes of this class are now extensively used for pumping purposes, and possess considerable advantages over those made of cast iron. They are more easily handled, and also cheaper, while sections of any reasonable length can be readily cut off and fitted wherever required. It has been found, however, in practice, that when dirty or acid water has to be dealt with, that cast-iron pipes are best. Pipes of large section should be made of mild steel, which is more homogeneous and possesses greater strength than wrought iron. The joint used for this class of pipe is somewhat different from that used in cast-iron pipes. Leaded joints are sometimes used when the pipes are per- manently fixed, such as in siphons, but they are not suitable for shaft work. Eadie's joint, which is somewhat similar, is also much used both for water and compressed air. At Kladno, Bohemia, a flange packing has been successfully adopted for a head of water of 1700 ft. One of the flanges is recessed to admit a ring of rubber or metal of [^ shape, this ring being held in position by a rigid metal ring, which gives great security and tightness to the joint (fig. 349). Expansion Joints, — Where the column of steel or wrought iron used is very long in either shafts or inclines, expansion joints should 298 PRACTICAL COAL-MINING. be used to prevent 'elbowing.' The commonest fomiB are merely jointa with an ordinary stuffing-box, containing hydraulic packing. The pipe entering the stulfing-bos should be perfectly smooth, and kept well greased. Pipe Supportt. — Pipes in a vertical shaft ought to be properly supported to keep them in a vertical line. It is also necessary to con- trive some support for the weight of a long column of pipes. A support ought to be put in every eight or ten fathoms at least. A Fio. 3<9. common method is to lay timber pieces across the shaft, and bolt them firmly down to the buntons at one end, and fix them into the strata at the other. Sometimes the rods are supported by the method shown in Ggs. 350, 351. Two cross pieces a a are laid across the pieces 6 b, the two sets of timbers being firmly bolted together with hanging and horizontal bolts. When there is little room in the shaft, the method FiOB. 350, 851.! — Pipe supports. employed is to use a gland, bent to the ctrelc of tlic pipes, with two screwed ends, over which a plate of iron is fixed. A piece of wood 0, like a saddle, may be fixed between the pipe and the support, and the gland then tightened by the nuts (figs. 352, 353). Size of Pipes. — The diameter of pipes will, of course, depend on whether they are connected to a lift or force pump, and on the velocity at which the water ia required to flow, Kor ordinary lift pumps the pipes ought to bo ^ in. larger than the working barrel, so that the bucket can be drawn through them if uecessary, and changed at the top of the lift or on the surface. With force or PUMPING. 299 plunger pumps this is unnecessary, and therefore, for this class of pump, the diameter of the delivery pipes may be smaller. The velocity of the flow of water in pipes varies as the area and area oo D^, therefore velocity oo D^. .', did^ : : \/i I ^2 or J=-j ; where <5x^fQ0=2O001bs. persq.in. 10x8 r -» 300 PRACTICAL COAL-MINING. (ft) Transversely: PxOax •7854 = ^xDx 3-1416 x/ PxlO =4xgxl6500 . p ^ tjii^}.^^^iQoo Iba. per sq. in. For safety, the working pressure would be taken at ^th to Jth of the aboye pressures. The thickness of pipes required can be obtained from the formula deduced from above, t= 2/ EXAMPLB. Given a head of water of 600 ft, and internal diameter of pipes 10 in. ; what thickness would the pipes require to be, taking this safe working pressure at (th I • 600 X 484 X 10 .R« . ^, ... . t= , = 'So in. or |tn m. 2 X 18500 X 1 ' Where the pipes are exposed to shock as in mine pumps, the practice is to make them with a greater thickness of metal than would be brought out by the foregoing formulae, which are based on the assumption that the pressure exerted is constant, and which takes no account of defects in casting, etc. The following rule will be found to coincide more closely with practice : — ^ = (•00022 Pd)+ -ISVrf (Molesworth). Where ^= thickness of metal in inches or decimals of an inch. P= pressure in lbs. per sq. in. due to head of water= A x '484. c{=dia. of pipe in inches. Taking the example as already worked out : — « = (-00022 X 600 X -434 x 10)+ '15 ,^^10= '5728 + •4740 = 1-046 in. For working barrels <= (-00017 ?d) + 1-26. To find the necessary thickness for wrought-iron pipes with a given head of water : — t='00002BS hd or ^= -0000666 Pd Weight of Cast-iron Pipes,—W=2'ib (D^ - d^) Where W = weight in lbs. per ft of pipe. D = external diam. of pipe in inches. (^= internal ,, „ 2*45 = constant. The weight of two flanges may be taken as approximately equal to one foot of pipe. In practice the thickness of pipes used is somewhat greater than the calculated thickness, to provide for wear and other contingencies. The following thicknesses of metal are used for cast-iron pipes of different diameter and for different heads of water: — PUMPING. 301 SOftHesd 100 ft Head ISO ft. Head 200 ft Head 250 ft. Head 800 ft. Head or 21*66 Ibt. or 43*3 lbs. or 64*85 lbs. or 86*6 lbs. or 108*25 lbs. or 129-9 Ite. Inside Press. Press. Press. Press. Press. Press. Diameter of Pipe. Thiclniess Thickness Thickness Thickness Thickness Thickness of MeUi. of Metal. of Metol of Metal. of MeUl. of MeUl. ins. ins. ins. ins. ins. ins. ins. 8 0-422 0*450 0-474 0 498 0-522 0-546 10 0-459 0-489 0-519 0-549 0-579 0-609 12 0-491 0-527 0-563 0*599 0-685 0-671 14 0-524 0-566 0-608 0*650 0-692 0-734 16 0*580 0-604 0*625 0-700 0748 0-796 18 0-589 0-643 0-697 0-751 0-805 0-859 20 0-622 0-682 0-742 0-802 0-862 0*922 24 0-687 0759 1 0-881 0*903 0-975 1047 Pump Valves or Glacks. — ^Valves for pumps used in mines are of yarious types, their design and construction depending upon whether the water is clean or gritty, acid or otherwise corrosive, and whether the temperature is high or low. There are three types of valves generally used, viz. : — Hinged yalves, commonly called clacks. Straight lift valves, which nae vertically on their seats. Flexiole valves, which alter their form on opening. In ordinary pumps the valves mostly used are of the hinged type, with either a single or double lid (see figs. 354, 356, 358). For direct-driven pumps, straight lift valves are very largely used. Figs. 356, 357 show such a valve, which is commonly used for any pressure up to 500 lbs. per square inch. Double flap or * butterfly ' lid valves are almost entirely used for buckets and clack valves of lifting sets. Thus the latter valve is very suitable for lifts which do not exceed 30 to 40 fms. ; but for lifts over 30 fms., iron hinges should be used instead of leather. Figs. 359, 360 show this type of valve. The valves are usually faced with leather, but where acid water has to be pumped, rubber is to be preferred, and sometimes vulcanite or brass is used instead of iron for mounting. If the water is hot a rubber composition is used for facing them. Hinged valves are more liable to leakage than straight lift valves, as they wear more unequally ; but the tightness of a valve depends a good deal on the pre^ure per square inch on its face, while the less bearing it has, the more difficult it is to keep it tight. On the other hand, the larger the bearing surface, the greater the wear. Leakage with hinged valves will probably amount to 10 or 12 per cent., and for lift valves 5 to 7| per cent. A valve should not be larger than 10 in. in diameter. If larger 302 PRACTIOAI. COAL-MINING, outlets than this are required they should be made double, for when the valve is very large it is impossible to prevent it from 'hammer- ing,' owing to the weight of water above. Good valves should be simple in construction, and not liable to get out of order. The; Fig, 3GG.— PUn. Fio, 367.— PUu. Common Hinged Clftck Vilve. Straight Lift Valve. Fios. 364, 256, 356, 3&7.~VBriuaa tjrpea of valves should present as little resistance as possible to the flow of water, and should close as quickly as possible on the completion of the stroke. Buckets. — ^Buckets are usually constructed of iron with leather mountings, the shell being often composed of gutta-percha, or a composition containing this. They are provided at the top with two flap lids opening from the centre. Their construction will be tmder- PUMPING. 303 stood from figs. 361, 362, 363. The leather and other mouatings should be of the very beat quality, otherwise they will rapidly wear, and cause much trouble and annoyance. For very high lifta the bucket is sometimes made entirely of metal. Fig. 364 shows such a bucket constructed of steel, and simply made to fit sufficiently well to prevent leaki^, and not oceasiou too much friction. >. 358.— Double hinged v^ve. Fia. 380.— FleiiblB v&lve plas Flo. 360.- Flexible vftlve elevation. Figs. 3G8, SES, 8S0.— Variaoi types of valvra. The bodies of buckets of this clasB are made a good deal longer than ordinary sorts, which increases their efficiency against leakage. Grooves are sometimes turned in the body of the bucket, and brass rings inserted to make them work smoothly. Flnngers or Bams. — Plungers for ordinary pit pumps are usually mode of cast iron ; for small pumps, or where the water contains much acid, they are sometimes made of brass or lined with it. The plunger is usually made hollow, and connected to the rods by the 304 PRACTICAL COAL-MININa. methods bLowq in figs. 366, 366. In large hollow plungcra the wood rod m Hometimes simpl; driven in firml; to give it sufficient gripping power to prevent it from slipping. The plunger should be accurately turned and finished smooth, so as to work with as little friction as possible. Plungers should be kept well greased at the top of the stuffing- box, aa this will reduce friction and tend to easy working. Pump.SodB or Bpears. — Pump-rods are usutdly made of pieces of pitch pine or oak, 18 to 45 ft. long, 30 ft being a common length, and square or rectangular in section, joined together by strong iron Fias. 3S1, 302, 363.— Bncket and connection*. plates to withstand the heavy strains to which they are subjected. Iron rods are sometimes used, but not very extensively, at least in Britain. They are more difficult to make and to put together, get more easily out of order, and are more difficult to repair than wooden rods. Speaking of iron pump-rods, Callon says : " The light- ness of rods is not usually a point to be desired, because we are often led, on the contrary, to give them additional weight. We may fairly conclude that this is one of those cases more frequent in practice than we think, in which the wotd modifinttian need not necessarily signify improvement, and that metallic rods have no decided superi- ority over wooden ones." PUMPING. 305 On the whole, rods made of pitch pine have been found to be in every way better suited for pumping. The aiie of section will vary according to the size of pump and length of lift. The pieces arc joined one to another either by a common square joint or a scarf joint, and held together by iron plates and bolts (see tigs. 367, 368, Flo. 864.— Steel bucket Fiob. S6G, 369.— PlUDgercoDDsctioDB. 369). For plunger or force pumps the joint should bo made square, as the whole of the pressure or work done is practically on the down stroke ; but for bucket or lift pumps, where the tension is greatest on the up stroke, the joint is often scarfed in a zigzag fashion which is found to give better results. For rods up to 8 in. or 9 in. square, two straps or plates and 2Q 306 f*ACTteAt CtfAt-MININO. ' dumb ' or ' clink ' bolts, pAt in ttt right angles fio the pbte bohe and a little above them (fig. 367), wiH be sirffictent to prevent tiie other bolts from tearing along the grain 6i the wood. The boH holes in the platea should be bored in zigzag fitthion, otherwise if they aiv Pius. 397, 368, 369. —PuuiJ- rods or spear joiots. placed in a lino tliey will have a greater tendency to split the rod. For rods over 9 in. square four plates will be necessary to give the requisite strength. The platea used on the joints are from 6 to 18 ft. in length, according to tlie size of the rods and the length of lift ; pnMMNO. 307 they may be either uniform in section or somevhat tapered at each end. Additional strength may be obtained by overlapping the ends of the rods, under the jointing plates, by a separate piece fitted in, and holding the ends by means of steel keys (a, fig. 370). Fio. 370. FioH. 371. 372. When the rods required for a pump have to be very large in section, and would be too large to be handled easily, two rods of smaller section are sometimes employed, braced together by iron stays and bolts, aa in fig. 371. 308 PRACTICAL COAL-MINING. Sometimes the lengths of pump-rods are joined together by plates having projections for the bolts (fig. 372), to obviate the necessity of boring bolt holes in the rods themselves. This plan is said to give additional strength to the rods, and saves labour in boring holes, and the plates are more easily put on. The same object may be attained by using two long wooden straps at the joint and bolting them firmly on the rod. In both these methods great care should be taken that none of the bolts get slack, as the rods would be liable to drop out from between the plates. The sizes of rods used, as already mentioned, will depend on the size and speed of pump, and length of lift or head of water. The following sizes are often used in practice, viz. : — 8-in. backet. Lift 30 to 40 fms. Rods 4 in. square, pistes g in. x 3) in. x 8 ft. Rod bolts 2 in. diameter. ' Dnmb ' bolts i in. diameter. Bolts put in 10 in. centre to centre. 10-in. bucket. Rods 5 in. square, with same sizes of plates and bolts as for 8-in. bucket. 12-in. bucket Rods 6 in. square, plates ) in. x } in. x 9 fU Rod bolts | in. diameter, dumb bolts g in. diameter, and five on each side of joint. 16-in. bucket Rods 8 in. square, plates i in. or g in. x 6 in. x 9 ft Rod bolts 1 in. diameter, dumb bolts { in. diameter. With a 20-in. bucket the rods would require to be 10 in. square, and four plates would have to be used instead of two, the plates being about | in. x 8 in. xl2 ft., and the bolts 1 J in. to 1^ in. diameter. Pitch pine sawn into lengths for pump- rods costs about 2s. 6d. per cubic foot. Plates bored and ready for putting on cost 8s. per cwt., and bolts 10s. 6d. per cwt. In calculating the size of rods and plates to be used for any given size of pump and length of lift, different formulae are used, giving somewhat different results, but a simple plan is to equate the opposing strains or pressures to which the rods are subjected. In an ordinary lifting-pump as illustrated (fig. 373), let /i be the tensile strength of pitch pine (12,000 lbs. per sq. in.) and A the sectional area of rod in square inches. Then the total upioard strain on rod will equal A x/. If a is the area of bucket in sq. in. (D^ x "7854), and p the pressure in lbs. per sq. in., due to head of water (h^ in ft. X *434), then a xp will be the total downtcard strain. Now A x/ shoula equal a x p or Fj = F2. This rule would give the data required for calculating the size of rod necessary to exactly balance the downward strain, but in actual practice a lam mar^u would have to be allowed for safety, this factor depending on the speed and size of pump. The inertia of the water column and of valves would also have to be taken into account. '* In large forcing pumps, with the engine placed on the surface, all the excess of the weight of the rods above that of the column of water, plus the friction, should be balanced, save a little surplus which is left to make the downward stroke begin distinctly. Not infrequently the main line of rods is over-weighted Fig. 878. puMpma. 309 on purpose, but at the same time balanced, in order to increase the mass set in motion. The object of this is to produce a moderate acceleration only at the commencement of the upward stroke when the steam has its full pressure and the power is much greater than the load, for it is on the rate of this acceleration that the reactions of the force of inertia which are got up in the yarious parts depend, and these reactions again increase the strain on the entire system." * It is generally allowed that the useful weight of the main rod ought to exceed by iV^h to Jth the weight necessary for raising the delivery valves in plunger pumps. For all practical purposes we may take the power necessary to overcome the friction of the water in moving through the pi|)e8 and valves, and other con- tingencies, at about |th of the power required to set the water column in motion, t.e. the total pressure exerted on the ram. To cover this the factor of safety should be comparatively high, sav 30 to 40 for quick-running, intermittent pumps, where the strokes are more frequent and the strain greater than in large slow-moving pumps, where the factor need not exceed 20 to 80. Example, — What size of (a) rod and (b) plates should be used in a 20-in. lifting set, the head of water being 40 fms. , ana the factor of safety 80 1 (a) Axf=axpx1A. A X 12000= 20* X 7854 X 240 X -484x30s=:81'8 sq. in. (area of rod required), or about 0 inches s<|uare. (6) The size of iron plates may be found in the same way, by substituting 50,000 1 for 12,000, the factor of safety being taken at 10. If two plates are put on each joint and each plate is 6 in. broad, A x 50,000 = 20^ X '7854 x 240 x '434 x 10 ; 5 A = 82*64. .*. A=6*52 sq. in. area ; hence Thickness of plate = |~ = 0'54 in. (about g in.). The plates would therefore require to be g in. x 6 in. x 12 ft. with bolts IJ in. diameter. For plunger pumps the compressive strain (6000 lbs. per sq. in.) of pitch pine would require to be taken instead of tensile strain. The following empirical formulfe are also used for determining the dimensions of pump-rods, plates, and bolts, where D= diameter of pump in inches. Bucket Pump-Rods : Sectional area of rods=^^ °^^^°^«* 84 ,. plates-*^ °^^^^^«* ,, „ bolts: D + 7 area of rod 10 Plunger Pump-Bods : Sectional area of rods of lowest lift= ^^ of pmnp ^ second „ ='"* °^ P°°'P+are> of bottom lift third „ = »■•«» of pump +are8 of second lift pl,te« =_?w»ofrod8 '- 10 bolts = »reaofrod« (o). (c). (9). These rolei are btsed upon the assumption that the lift is not greater than 60 to 80 yards. * Lectures on Mining, by M. Gallon, vol. iL p. 363. t Tensile strength of wrought iron =60,000 lbs. per sq. in. SIO PBACnCAL OOAL-UIKINQ. Guiding the Pump-rod'. — When the pump-rodB are in operation, they require to be kept from twisting or vibrating in the shaft ; this is done h; ' collaring '.or guides. The collaring is composed of pieces of wood nailed or bolted to the cross buntons at certain fixed distances apart. They ought to i>e placed sufficiently near each other to keep the rods from ' buckling ' under compressive strains, and they ought to be kept in line or as nearly so as possible. Pieces of hard wi»d, oak, or beech, called cleats, are fixed to the rods (an, fig. 374) either by nails, counter-sunk bolts, or by glands at the top and bottom. Elevation. PIftn. FiQH. 374, 876.—' ColUring' for rods. These cleats arc 2 in. to 3 in. thick, tapered at the en<^ and made a little longer than the stroke of the pump. They are put on to prevent the rods from wearing too rapidly, and to prevent breakage. Figs. 374, 375 show the methods of collaring. Sometimes a piece of wood, square in section, is filed to the rod& and works in a ' shoe ' fiied on the cross buntons or the guides, or the rods may be made of iron and a ' shoe ' fitted to suit, which. » much more substantial. All these cleats or rubbing pieces should be kept well lubricated^ to reduce friction and wear to a minimum. The rods working inside- the pipes (called 'wet' rods) must also be provided with cleats to> prevent the bolts or plates from rubbing against and wearing the pipes. PUUPIMO. 311 *Bang^ Piecet.—The rods should also be provided with 'baog' pieces, hj means of which, in the event of the roda breaking or getting detached from the engine for repairs, the; may be caught and rested ou strong' beams placed across the pit (called ' borse trees '). The ' bang ' pieces (figs. 376, 377, 378) may be made of either wool or iron clamped to the rods. It is best to secure these cat«hes to the rods without the bolts passing through the latter, because then FiOB. 878, 377, 378,—' Bang' jiiecea. they can slip a little, and so lessen the shock it they happen to fall away. With the same object a 'cushion' is sometimea used, made of thin boards {a a ) placed immediately above the ' horse trees. ' The croes beams or ' horse trees ' require to be sufficiently strong to withstand the shock of the column of rods falling on them suddenly. There ought to be at least two of these supports, one immediately below the 'bell cranks,' and the other at the Ixittom of the rods. OJgett or Aprone. — The usual method of operating two sets of 312 t>llACTlCAL COAL-MlNINti. pumps by one colunin of rods is generally done by meaUs of offseta called aprons. The usual way is to insert a square block of vood) called an 'apron,' between the two sets of rods, sq as to carry the one set (those of the lower lift) clear of the working barrel of the other set (figs. 379, 380). Cast-iron aprons are also t»ed for making offsets (figs. 381, 382), and are better than wood, as they are lees liable to shrink, and the clamps leas likely to get loose. They are, how- ever, more expensive and more difficult to fix. Guides or collaring should be placed as near where the oftset is made as possible, both above and below. The offset may also be effected by using a ' croes-bead,' which is to be preferred to the ordinary apron, as the set of rods operated FDUFINO. 313 below the croBs-heod is in direct line with the rods working above, bo tending to reduce friction and strains (see fig. 383). Baiancinif tlt« Rodi. — In most pumping arrangemente where wooden rods are used some balancing arrangements are required, as the rods are nearly always heavier than the column of water they have to raise. Gallon says : " This excess of weight requires the expenditure of a certain amount of motive power to raise it, and as soon as the rod in its descent has opened the clacks it becomes useless and even Fio. S8S.— Cross-head. Via. 884.— Balance beam. injurious. In fact, it becomes necessary to counterbalance it, so that the rod may not acquire an accelerated velocity."* There are dilferent methods of applying a counterbalance, but the commonest one is to use a balance on the ' bell-crank ' at the surface, or an auxiliary bell-crank in some part of the shaft. A double bell-crank is sometimes used for the counterbalance, and at one end a heavy weight is placed, generally a large box filled with scrap metal, which can be adjusted whenever required (fig. 384). Hydraulic or loaded pistons are also used for balancing the rods, ■ Ltdurea on Hining, M. Gallon, vol ii. Jip. 317-8. 814 PRACTICAL COAL-MINING. and compreBsed air, where used, can also bo applied for this purpose, and ia to be preferred to the hydraulic piston. In West and Darlington's hydraulic balance an auxil- iary piaton is used, worked off the main rods (fig. 385). The loss of water is made up by the pipe h, which communicates with a cistern placed in the shaft. When this cannot be done a small plunger J draws up and forces in the necessary supply. The same arrange- ment can be adopted with compressed air.* Bucket Pumpt. — These pumps are lately used for raising water in shafts. They are similar to ordinary well pumps. A working barrel a (fig. 387), smoothly bored out, works the bucket b. Immediately below the working barrel is the clack piece c, which contains the suction or receiving clack ^ ^ '^^ . -034 j 144 \ 144 I Where D= diameter of pump in inches. L=: length of stroke m feet. N = number or efiectiYe strokes per minute. 6 = Gallons delivered per minute. 6 '26 = number of gallons in 1 cub. ft. of water. These formulae will give the theoretical quantity delivered, 5 per cent to 12 per cent of which should be deducted for slip at the valves and bucket or plunger. Example. — How many gallons could a pump 15 in. diameter, with a 6 ft. stroke, and making eight effective strokes per mmute, deliver per minute, allow- ing 10 per cent for slip % G=Dax-034xLxN = 15,x -034x6x8 = 369 '2 gallons per minute without slip. Q A7 '9 w on . •. G" "^--s 880 -48 gallons per minute allowing for 10 per cent slip. The theoretical quantity delivered per foot stroke is approximately found by ^ 80 the expression G = -^- 318 PRACTICAL COAL-MINING. The diftmeter of pump reqnired for a certain qaantity of water may also be derived from the above formula, G D»= •084xLxN' Example, — What size of pamp would be required to deal with 10,000 gallons of water per hourf Engine to work 124 hours per week, and 10 per oent to be allowed (or leakage. 10,000 gallons per hour =166*6 gallons per minute. 124 hours per week= 17 '7 hours per day. . ^^^'^^24 ^iQ^j ^^^ -, 248 -48 gallons per minute. If the effective speed of pump is 80 ft per minute, then D«= ;f^° L~15'6 in. diameter. The '^ ^ '^ ' *034x80 size of pump required would therefore be 15*6 in. diameter, say with 5 ft stroke, going at six strokes per minute. Plant Bequired for Working Pumps. — The engines used for operating pumps may be worked with steam, compressed air, hydraulic pressure, or electricity. For operating pumps in shafts, engines worked by steam are almost universally used, especially when they are situated on the surface. Steam engines for working pumps by means of rods may be divided into three classes : rotative, non-rotative, geared. The non-rotative types may be either direct-acting or indirect- acting. Direct-acting engines are those in which the piston-rod is in line and connected to the pump-rods. The Bull engine is the most familiar type of this class of pumping engine. Sometimes a direct-acting engine is defined as a "machine for raising water, so constructed that the pump is worked by the motive- power cylinder, without the intervention of beams, connecting rods, cranks, or fly-wheels." Direct-acting engines are not so largely used now as formerly, unless for large quantities of water, or deep shafts, because the cylinder usually obstructs the mouth of the shaft. This is often inconvenient, imless there is plenty of room, or a shaft is wholly set apart for pumping. This type of engine also requires very heavy and expensive foundations, and it is also wasteful of power, owing to the uncertainty of the point at which the stroke is completed, and the necessity for thus working with a large ' clearance ' space in the cylinder. Geared pumping-engines are very largely used for actuating pumps with rods, and are receiving more attention from engineers than formerly. The great advantage of this class of engine is that the speed can be easily altered to suit any conditions and that the work per stroke can be varied much more easily than in other types. It must not be forgotten, too, that steam, being a much more clastic body than water, can be moved more rapidly without danger, and hence in a geared engine the steam may be moving very rapidly, while the water may be moving veiy slowly. This class of engine can likewise be erected more cheaply and disposed of more readily than large direct-acting engines, if not required for, or readily adapted to, other work than pumping. Special Types of Pumping £ngii engine may be termed a Cornish engine, ' the cylinder instead of over it (tig. 388). The cylinder is placed directly over the shaft in a line with the pump-rode, these being a continuation of the piston-rod, and acting direct. The great objection to this class of engine ia, that it blocks up the shaft and requires lai^e and expensive foundations. On the other hand, the first cost is less than for an ordinary Cornish engine. Fio. 388.— Ball engiDCi. Fio. 3S9.— Cornish engiDe. A modification of the Bull engine is sometimes used, in which, to avoid the cylinder being placed directly over the shaft, it is placed some distance back and bell-cranks introduced between the piston and the pump-rods. In this way the space in the shaft ia not encroached upon te the same extent, and less expensive foundations are necessary. Sometimes these engines are worked on the compound condensing principle, with high- and low-pressure cylinders. The steam is regu- lated in the same way as in the Davey engine, by an auxiliary piston and tappet valves, and is not permitted to act by expansion alone, but by mre-tiramng te a considerable extent. Comith Engine.— This is one of the oldest of pumping engines, the type having been first devised by Watt, and anch engines are still used to a considerable extent for pumping in mines (fig. 389). The Cornish engine is gener«lly worked as a single acting, high-pressure 320 PRACTICAL COAL-MINING. condensing engine. It consists of a vertical cylinder, having the piston-rod connected to one end of a large ' walking ' beam, and the pump-rods to the other end. The beam usually works on a fulcrum near its centre, thus causing the stroke of the engine to be somewhat longer than that of the pumps, and the flow of water in the pipes is therefore less than the speed of the steam piston, in order to lessen the shock of the water in the pipes on the sudden closing of the valves at the reversal of the stroke. In the working of the engine steam is admitted at the top of the cylinder, this causing the piston to make its down stroke. The steam is then cut off and an equi- librium valve opened by means of a tappet-rod, which allows the steam to pass to the under side of the piston, thus equalising the pressure and causing a pause in the movement. The weight of the rods alone is sufficient to cause the down stroke and force the water up. The steam is then exhausted into the condenser, where a vacuum is formed by the air-pump. This process is repeated at each stroke. The engines are best suited for slow speeds and long strokes. They are very expensive at first, but once set up they give little trouble, require little repair, and give a high efficiency. Barclay Engine, — This is another well-known type of the beam pumping engine, which is much used for dealing with large quantities of water. In construction it is a modification of the Cornish engine. It consists of a single steam cylinder placed vertically, the piston rod being connected to the overheiotd beam. To one end of the beam the pump-rods are connected, while the other end works on a fulcrum which takes the form of a rocking pillar. Near to the centre of the beam a rod connection is attached for working the air pump and condenser hot- well. This type of engine, like the Cornish, is best suited for large quantities of water and where a long stroke can be adopted. Owing to the arrangement of the beam the stroke of the engine is less than that of the pumps : for instance, the piston stroke may be 8 ft., while the pump stroke may be 10 ft. Engines of this type are made with cylinders 50 to 100 in. diameter and 8 to 12 ft. stroke, moving at two to four strokes per minute. Another type of engine much used for pumping in the Fifeshire coal-field, where large quantities of water are met with, is one in which a pair of cylinders, high- and low-pressure, working compound and condensing, are placed vertically directly over the shaft, the piston rods of the cylinders being connected direct to the ends of the bell- cranks which operate the pump rods. These engines are well suited for raising large quantities of water, 1000 to 1500 gallons per minute, from depths of 150 to 250 fms. At the present time a plant of this type, with cylinders 58 and 100 in. respectively, is being put down to raise 1200 gallons from an expected depth of 350 fms. The objections to this type of pumping engine, like the Bull engine, are that the cylinders are placed directly over the shaft, and they take up a great deal of space, necessitating the sinking of PUMPING. 321 a very large shaft, or devoting a shaft entirely to pumping. They are best suited for large rectangular shafts where the necessary space can be set apart for them at one end of the shaft. Wherever large pumping engines of the types just described are employed it is almost imperative that a duplicate plant be installed to deal with the water in the event of any serious breakdown. This duplicate plant may consist of a direct-acting pumping engine, such as the Riedler pump, placed underground at the bottom of the shaft to force the water direct to the surface. Hi/rizontdl Pumping Engines, — A typical pumping plant of this description is at work at Boghead Colliery, Bathgate, N.B. The plant is designed to deal with 500 gallons per minute from a depth of 160 fms. It consists of high- and low-pressure cylinders placed tandem (fig. 390) 38 in. and 76 in. diameter respectively, each Condenser H.P.C. L.P.C. Elevation I : ! i i! i ' ! i ■■'■A A I'lA ^ Urhki Fio. 390. — Direct-acting horizontal pumping engine. cylinder having a stroke of 9 ft. The piston-rod of the low-pressure cylinder is continued forward and connected to the bell-cranks, while the piston-rod of the high-pressure cylinder is continued back- wards to the condenser and air-pump. In this case no fly-wheel is used. The pumps are worked by a double set of rods attached to the bell-cranks at the surface, each set of rods working two plunger and one bucket lift at three different stages in the shaft. At the top and mid lifts the offsets are made by means of cross-heads bolted to the rods and connected to each other by iron side rods far enough apart to clear the pumps. The details of the pumps are as follows : — Two bucket lifts at pit-bottom, 160 fms. from surface, each set 141 in. diameter, lifting 30 fms. ; two plunger lifts at 130 fms. each 19| in. diameter, lifting 56 fms. ; two plunger lifts, each 20 m. 21 322 PHACTICAL COAL-MINING. diameter, at 74 fnis., lifting to the surface. The sizes of pump-rods for the various lifts are :— bottom bucket lifts, rods 6 in. square ; second lift, rods 12 in. square ; top lift, rods 14 in. square; the iron strapping plates at the joints for these two latter are 11 x f in. x 17 ft. The available steam pressure is 90 to 100 lbs. per square inch, plus 12^ lbs. vacuum from condenser. A good type of pumping engine is one in which high- and low- pressure cylinders are used. The connecting rods to the bell-cranks are in a direct line and form a continuation of the piston-rod. A back piston-rod works a fly-wheel which imparts steady motion to the engine. This class of engine has much to recommend it for pumping purposes, as it works very smoothly, and can be easily regulated to any required speed. Geared pumping-engines are very largely used for pumping water at collieries, and, as has already been pointed out, are peculiarly fitted for such work, and have many advantages to recommend them. They may be constructed either with one, two, or four cylinders, and may be condensing and compound. The gearing can be altered to suit any speed and any size of pump. This easy adaptability to work under varying conditions makes these engines very suitable for mining, and gives them many advantages over the larger types of vertical engines. An engine constructed in this way gives a high efficiency and a small consumption of steam, and works very smoothly at almost any reasonable speed. Fig. 391 shows the arrangement of a geared engine with low- and high-pressure cylinders, as used at the Priory Colliery, Blantyre, where the water has to be raised from a depth of over 200 fms. The high- pressure cylinder is 20 in. diameter, and the low-pressure cylinder 34 in. diameter, with 5 ft. stroke geared to about 2| to 1. The cylinders are steam-jacketed, and work with a very small consump- tion of steam. They can be regulated to any speed, as low as 1^ strokes being attainable. At Holm Colliery, Kilmarnock, the pumping engine is constructed with quadruple cylinders, two high-pressure and two low-pressure ones being supplied. The high-pressure cylinders are 16{ in. and 15 J in. diameter respectively, while the low-pressure cylinders are 24^ in. and 26 in. diameter respectively, the stroke being 3^ ft. and the gearing 5^ to 1. The water is raised the first 68 fms. by two rams 15 in. diameter and 5 ft. stroke, the lower lift of 13 fms. being two buckets 10 in. diameter and 5 ft. stroke. The speed is five strokes per minute, and the water raised 420 gallons per minute. Direct-acting Steam Pumps Underground. — Direct-acting pumping engines placed underground are very largely superseding surface engines with heavy pump-rods working in the shaft. The greater simplicity of construction and cheapness combined, make them desir- able for pumping purposes, and although, as a rule, they require much fuel, this ia compensated for in other ways. These engines are nearly always double-acting, and are directly coupled to the pump. They may also be made to work geared, but this arrangement is not so much employed underground as the direct-acting. Double-acting pumps have generally a comparatively short stroke, with very much smaller masses to move them than pumps actuated Fio. 391. — Geared pamping eogine. from the surface with rods, and they can therefore be driven at much greater speeds. The higher speeds at which they can be driven, combined with their smaller size, are the main features which commend this class of pumpa for use underground. DirecUlriven steam pumpe are now iised for heads of water varying from 200 to 1800 ft. Where engines are placed underground, a large lodgment, sufficient for, at least, a week's water, ought to be provided, to give time for rep^re on the engine should they be necessary. With engines placed 324 PRACTICAL COAL-MINING. underground, the following are some of the main advantages to be gained : — The necessity for heavy pump-rods, which are expensive at first cost and for upkeep, is done away with. As no pump-rods are required, less shaft space is occupied. The engines can be worked at high speeds, as there are no heavy rods to put in motion at the commencement of each stroke, and the work is evenly distributed. The flow of water being continuous, smaller pipes can be used in the shaft. On the other hand, there are the following disadvantages to be kept in view : — Steam must be taken underground or boilers fitted up in the workings, both of which methods are more or less bbjectionaole ; especially the latter. The engine is liable to be drowned by a sudden inflow of water (the same, however, may be said of any other type of pump operated from the surface). Loss of steam by condensation and difficulty of dealing with the exhaust steam. Increa.se in temperature of air if placed near the intake, and consequently injurious effecte from the moisture to the roof and timber of roadways. The use of steam in confined places is attended with danger. Piston Pumps. — This type is largely used for direct-acting punips working underground without rods, and is invariably double-acting. Fio. 392. — Piston pump. The working of the pump will be understood from fig. 392. A piston a works in the barrel ^, to which arc four openings fitted with valves, two receiving and two discharge. The action of the pump is as follows : — When the piston moves outward, the clacks or valves c and e will, supposing the pump is full of water, be open, water being received through the valve c and discharged through the valve e. On the return or inward stroke the valve tl will be open, receiving water, and the valve / open discharging, so that there is a continual flow of water during both strokes. There are so many steam pumps in the market, all equally suitable for underground work, that it is diflScult to select any particular PUMPING. 325 make for detailed description. The general principle of a double-acting steam pump will be seen from fig. 393, in which the steam cylinder is connected direct to, and is in line with, the double-acting piston pump, provided with an air vessel on the delivery column. Delivery Column len^ery valve Suction Valve Fio. 893. — Double-acting steam pump. Worthington Pump, — This is a well-known type of direct-acting steam pump for underground work. It consists of a steam cylinder with piston (A, fig. 394), the piston-rod of which is continued and Fio. 894. — Worthington steam pump. directly connected to a double-acting plunger B, in the water cylinder or pump. The steam is admitted to the cylinder by an ordinary slide valve E, working upon a flat face over the port-holes. The valve receives its motion from a vibrating arm F, which swings through 326 PRACTICAL COAL-MINING. the whole length of the stroke, with long and easy leverage. As the moving parts are always in contact, the blow inseparable from the tappet system is avoided. The double-acting plunger B works through a deep metallic packing ring, bored to an accurate fit. Both the ring and the plunger can be quickly taken out, and either refitted or ex- changed for new ones ; and if it is desired at any time to change the proportions between the steam pistons and pumps, a plunger of smaller or larger diameter can be readily substituted. The water enters the pump from the suction chamber C, through the suction valves, then passes partly around and partly by the end of the plunger, through the force valves, nearly in a straight course, into the delivery chamber D. The valves usually consist of small discs of rubber or other suitable material. The plunger is located some inches above the suction valves, to form a settling chamber, into which any foreign substances may fall below the wearing surfaces. Two steam cylinders and two pumps are usually cast together to form one machine. The right-hand division moves the steam valve of the left hand one, and vice verftd ; under this arrangement one pump takes up the motion when the other is about to lay it down, thus keeping up a uniform delivery of water. Biedler^s Pump, — The main feature in this pump is that the valves are aided in their movementa by mechanical means, and so nearly perfect action is secured. The valves are constructed so as to open freely without any mechanical aid, but a little before the time when they should close entirely, w^hen the velocity of the water is con- siderably reduced so that a partial closing will offer no appreciable obstruction, a lever or rod operated by valve gear from the crank- shaft moves forward and closes the valve ; the arm then recedes and removes the pressure from the valves before the time for opening arrives. The valve gear is constructed in various ways, and may be operated by levers, cams, or eccentrics. Fig. 395 shows the main outlines of the pump. These pumps are' driven direct, and although they cannot be driven at such high speeds as some other types of steam pumps, they can be worked very successfully for very high lifts up to 2000 ft., and pump 600 to 800 gallons of water per minute. A Riedler pump has recently been installed as a duplicate to the large pumping engine on the surface at the Aitken Pit, Kelty, Fife, to deal with 1500 gallons per minute against a head of over 1200 ft. Davey^s Differential Engine. — This engine is also largely used for pumping purposes. The main requirements to be satisfied in a good pumping-engine are economy in consumption of fuel, safety in working, and immunity from stoppages. The distribution of steam should be effected in such a way as to cause no shock or slip in the pumps ; and in the event of a sudden casing of the losid, the engine should be safe ; in short, it should be self-governing under extreme variations of conditions. To secure this, the Davey Differential Valve Gear, which admits steam to the 328 PRACTICAL COAL-MINING. engine in proportion to the resistance to be overcome, and, in case c sudden total loas of load, reverses the steam to catch the piston, < designed. The action of the gear will he understood from fig. 396 The main slide valve G is actuated hy the piston-rod through a lever H working on a fixed centre, which reduces the motion to the PUMPING. 329 required extent and reverses its direction. The valve spindle is not coupled direct to this lever H, but to an intermediate one, L, which is jointed to the first lever at one end ; and the other, M, is jointed to the piston-rod of a small subsidiary steam cylinder J, which has a motion independent of the engine cylinder ; the slide valve I being actuated by a third lever N, coupled at one end to the intermediate lever L, and moving at a fixed centre P at the other end. The motion of the piston in the subsidiary cylinder J is con- trolled by a cataract cylinder K on the same piston-rod, by which the motion of this piston is made uniform throughout the stroke, and the regulating plug Q can be adjusted to give any desired time for the stroke. The intermediate lever L has not any fixed centre of motion, its outer end M being jointed to the piston-rod of the subsidiary cylinder J ; the main valve a consequently receives a differential motion compounded of the separate motions given to the two ends of the lever c. Thus the cut-off can be suited to different loads which may be on the engine. Riedler Differential Pump, — A differential pump is practically a double-acting pump with only two A^alves. By an arrangement of the parts, an equal amount of work can be done on each side of the steam piston during one revolution. In a double-acting pump four valves are required, viz., one suction and one discharge valve for each end of the double-acting plunger. A differential pump has the advantage of always being primed, as will be seen by referring to fig. 397, where the column pipes D, the discharge space C, and the differential plunger chamber are always in connection. Thus the total pressure due to the water column is always on the differential plunger H. In other words, as long as there is water in the pipe, the pumping engine will always have resistance to overcome, even should suction be deficient. The arrangement, therefore, prevents undue severe hydraulic stresses on the different parts. As it has only half the number of valves, this form of pump is simpler than the double-acting pump, and is used, in all cases, until the capacity becomes too great, so that the valves are cumbersome. When this condition obtains, it is better to use a double-acting pump instead, which would be half the size of a differential pump of the same capacity. In working, the water enters the suction pipe A, passes into the suction air-chamber, and thence into the suction funnel B. When the main plunger J moves towards the steam cylinder, it draws in its displacement of water through the suction valve E, and on its return stroke, the suction valve having been mechanically closed, it forces a volume of water equal to its own bulk through the discharge valve F, half of this water passing out into the main pipe D, the other half passing down and following the differential plunger H. The discharge valve F being now closed, th« main and differential plungers, which are connected by means of side rods, again move 330 PRACTICAL COAL-HINING. towards the engine, the main plunger drawing the water through the suction valve as before (E), the ditferential plmiger thus dis- placing B. body of wat«r equal in bulk to its dtsplacemetit, and forcing it through the discliarge pipe C into the main D. The cross-sectional areas of the main and differential plungers are generally made in the proportion of nbout two to one, HO as to equalise the work done, as is the case in a double-acting pump. The rods G are the side rods connecting the cross-heads of the main and PUMPING. 331 differential plungers, these rods being always in tension. In front of C, and connecting to the main pipe D, is a clack valve (shown open). The valve is for the purpose of preventing the water in the pipe from running out when it is desired to remove the valves or examine the interior parts of the pump. This valve is kept open when the pump is working, but can be shut when required bj means of levers on the outside of the clack chamber. Water Tank =-^^^ ^hS^? G H Fio. 398. — Moore's hydraulic pump. Mooters Hydraulic Pump, — In this pump no rods are used, two columns of water being substituted for the ordinary solid rods con- necting the steam engine to the pump. The action of the pump will be understood from fig. 398. On the surface is a cylinder A B, in which travels a piston P, driven by the tumbling crank of a steam engine. Underground there is another cylinder C D, exactly similar to the first. The piston Q, which travels in it, is connected to an ordinary double-acting pump. There are pipes F from the ends A 332 PRACTICAL COAL-MINING. of the first cylinder A B to the end D of the second C D, and another, E, from the end B to the end C. The pipes and the cylinders are both kept full of water. When the surface piston makes its first stroke, the water is forced out of one end of the cylinder through the pipe to the corresponding end of the cylinder underground, and the piston is then driven back from C to D. When the stroke on the surface is reversed, the piston imderground is forced in the opposite direction, and the motion is thus transferred from the engine on the surface to the pump underground, in the same way as would have been done had there been two rods instead of two columns of water. Should there be any leakage in one of these pipes, the plunger at the bottom would make a shorter stroke in the one direction than in the other, and would work towards the end, and unless there was some regulator, would knock the end of the pump off. This is obviated by having valves work by tappets, set at such a distance that, when the stroke is completed, they are opened, and the water allowed to pass from one pipe to the other, thus adjusting the stroke of the rams. Curves based on the work done by one of these pumps 10 in. dia- meter, showed an efficiency of 66*26 per cent. The energy lost in the friction of the engine gearing and surface power rams was 10*24 per cent. ; in transmitting the power through the pipes 14*36 per cent., and in the friction of the underground rams 9*12 per cent. These figures compare favourably with the efficiency of pumps operated by electricity or compressed air. This hydraulic pump can work with a column of water of 150 fms. or less, but more satisfactory results are got when the column is between 40 to 80 fms. When it is too great, much trouble ma^ ensue, and the pipe joints become very difficult to keep tight, while the pipes themselves are apt to burst, especially at bends. Again, at long distances (say over a mile underground) these pumps do not work satisfactorily, and in such cases it is better to employ either electricity or compressed air as a motive force. Katelowsky Pump, — With this pump a combination of hydraulic pressure and compressed air is used. The system includes at the surface : (1) a steam engine M (fig. 399) operating the water- compression pumps P and the air-compressor C, the latter furnishing the air for the pressure regulator R. Underground the plant con- sists of : (a) an hydraulic motor K, of a special form, operating the lifting pumps G ; {b) two pressure regulators, R^ and R^, for the water pipes. In the shaft : (a) The pipe 1, conducting the water to the pumps ; (6) the pipe 2, carrying the water discharged or exhausted from the pump ; (c) the pipe 3, carrying compressed air to the regulators ; {d) the pipe 4, for the water lifted or discharged from the mine. The water operating the pumps passes from the pump P, through the accumulator A, which regulates the pressure through the pipe 1 to PUMPING. 333 the motor K at the bottom of the shaft. After performing the work it is returned to the surface through the pipe 2 on which is the regulator R', and is discharged into the reservoir S, from which the pump P' is supplied. The regulator, as shown, is formed of two cylinders, C, and C^, in which are two pistons, P, and Pj, of such diameters that the ratio between them is 1 : 10. The wator acting on P, with a pressure, say, of 200 atmospheres (3000 lbs. per sq. in.) is counterbalanced hy a compressed air pressure at 25 atmos- Fio, 3»9.— KMelowskj pump, pheree (376 lbs. per sq. in.) or P^. The piston is a hollow cylinder of phosphor bronze. The water piston P, has a small cavity a, which permits the escape of water in case the pressure rises too high and causes the piston Pj to rise too high. Several pumping plants on this system have been iustallcd at collieries in Germany, where they have given a useful effect of 69 to 75 per cent. The principal advantages of this method are the small size of the different parte, both fixed and moving, and the ability of the pump to work when submerged, which is impossible with steam. On the other hand, it is rather an expensive system of pumping. 334 PBACnCAL COAL-MINING. Pnlsometer Fump. — The Pulsometer is very largely used for pumping water under TariouB conditions, particularly when the lift is Bmall. It will work best, and give the greatest efficiency, when the height to which the water is to be raised is between 30 and 60 ft. It is very suitable for drainage oF dip workings, or sinking shafta, or Fio. 400. — Pulsometer pump. for raising wator from settling ponds to coal-washing machines, as it can work fairly well with dirty or gritty wator. The pulsometer is entirely different in construction from an ordinary steam pump, inas- much as it has no steam cylinder, pinton, piston-rod, or bucket. Its construction may be understood from the accompanying illustration in fig. 400. PUMPING. 335 The body consists of a casting shaped somewhat like a pear, and divided into two chambers A A joined side by side, and with tapering necks bent towards each other, surmounted by another casting called the neck J, accurately fitted and bolted to it, in which the two passages terminate in a common chamber, wherein is fitted the ball- valve I, which can oscillate between seats formed at the junction of the neck. Downwards, the chambers A A are connected with the suction passage C, wherein the inlet or suction valves £ E are arranged. A discharge chamber, common to both chambers, and leading to the discharge pipe, is also provided, and this also contains one or two valves F F, according to the purpose for which the pump is required. The air-chamber B communicates with the suction. The suction and discharge chambers are closed by covers H H, accurately fitted to the outlets. These can be readily removed when access to the valves is required. StaHing the Puhometer, — ^To set it at work, the pump is filled with water, either by pouring water through the plug-hole in the chamber, or by drawing the discharge. Steam being admitted through the pipe K, by opening the stop-valve to a small extent, it passes down that side of the neck which is left open to it by the position of the ball, and presses upon the small surface of water in the chamber which is exposed to it, depressing it without agitation, and con- sequently with very little condensation, and driving it through the discharge opening and valve into the rising main. The moment that the level of the water is low enough to uncover the horizontal orifice which leads to the discharge, the steam blows through with a certain amount of violence, and being brought into intimate contact with the water in the pipes leading to the discharge chamber, instantaneous condensation takes place, and a vacuum is in consequence so rapidly formed in the newly emptied chamber that the steam ball is pulled over into the seat opposite to that which it occupied during the emptying of the chamber, closing its upper orifice and preventing the further admission of steam, and making the vacuum complete until water rushes in, as it does immediately through the suction pipe, lifting the inlet valve £ and rapidly filling the chamber A again. The condition of things is now exactly in the same state in the second chamber as it was in the first, and similar effects are therefore obtained. Small air-cocks are screwed into the cylinders and air-chambers, to prevent the too rapid filling of the chambers on low lifts. While the pulsometer is admittedly a handy and useful pump under various conditions, it lias the drawback that it consumes a large amount of steam for the work done, compared with direct-acting steam pumps. For instance, a pulsometer raising 100 gallons of water per minute, to a height of only 26*25 ft., required 29*7 lbs. of coal per H.P. per hour, which is a very large consumption, considering the conditions. 336 PRACTICAL COAL-MINING. A good deal of difficulty is also sometimes experienced with the steam hall valve getting worn flat in some places and sticking. Centrifiigal PumpB. — Centrifugal pumps have heen long used as hlowers for air in forges and furnaces, and are now largely used for raising water to moderate elevations. They are particularly well adapted for disposing of dirty gritty wat«r, such as the dis- charge water from coal-washing machines, or where the water from machines has to he used over again, providing the height he not too great. They will work under such conditions much more efficiently than pulsometers. The construction of the pump will he imderstood from fig. 401. Inside a flat casing of approximately circular outline are the paddles or hlades, which extend from near the centre outwards to the cir- cumference, and are usually curved backwards. The water between the blades tends, in virtue of the centrifugal force, to move outwards, and is allowed to pass off through a large dis- charge oriflce tangential to the circle described by the paddles. The height to which water can be raised, if there is no loss, by centrifugal pumps, may be ex- pressed by the formula h = —- j Fio. 401. — Centrifugal pump. in practice, however, /* is only equal to alx)ut J ^ . The velocity of the blades is usually taken atN=10^/i. Centrifugal pumps, to work well, must have a very short suction pipe, or, what is better, have the water flowing into them, or be submerged altogether in the water to be raised. If not submerged, they ought to be primed with water before being started, otherwise, in driving the air out of them, they simply act as a blower. With the type of centrifugal pump just described only a very limited head could be dealt with, 50 to 100 ft., and even with this a low efficiency was generally the result. The problem was to get a centrifugal pump that would pump water against a head of a greater PUMPING. 337 height than 100 ft., say 500 to 1000 ft. This has now been accomplished by running centrifugal pumps in series. Thus if an ordinary single pump can deliver water against a head of 40 ft., the addition of another chamber will give a final delivery of 80 ft., while three chambers will enable the pump to discharge the same quantity of water against a head of 120 ft. In collieries where frequently large quantities of water, often dirty and gritty, have to be dealt with, such pumps are of great utility. The writer recently saw centrifugal pumps, of the Gywnne type, dealing with 500 to 600 gallons of water per minute against a head of nearly 300 ft., and they gave very little trouble. Messrs Mather k Piatt, of Manchester, have recently introduced a high-lift centrifugal pump, capable of discharging water against a head varying from 250 to 500 ft. ; several of these pumps being at work in Scotch collieries. This machine (fig. 402) is known as the * Patent High-Lift Turbine Pump,' and its main feature is that it consists of one or more sets of vanes, or impellers, each set running in its own chamber, but upon a common shaft, the delivery pressure of the water varying directly as the number of chambers iised. In Mather k Piatt's patent centri- fugal pump the water enters the revolving wheel axially, traverses the curved internal passages between the vanes, and is discharged tangentially at the periphery into a guide ring of special construction ; this conveys it to the annular chamber in the body of the pump, where the velocity head imparted to the water by the wheel is converted into pressure head. From this chamber the water is finally discharged into the delivery pipes, or, if the pump be a multiple one, into the second and subsequent chambers. A special feature of this pump is the provision of the stationary guide ring mentioned above ; this is fixed concentric with the revolving vanes, and, owing to its design, enables the conversion of velocity into pressure head more perfectly than hitherto, thus increasing the possible height of lift and efficiency of the pump. There can be no doubt that pumps of the types described have advantages over the ordinary plunger pumps so largely used in mining work, and they are specially useful for dip workings. They can be easily moved into a new position with the extension of the workings, which in itself is a great advantage. Other advantages claimed for these centrifugal pumps are : — They have few moving parts in contact, thus reducing wear and tear. As they can be designed to ran at a high speed, they occupy little space. Heavy foundations are unnecessarv, as even large pumps can be fixed to wooden beams or fixed on a moving bogie. They can deal with dirty and gritty water more efficiently than the orainary ty]ie of steam pump. The following formuUc are used for calculations with centrifugal pumps : — 22 PRACTICAL COAIi-MINlNG. PUMPING. 339 (I.) To find the required peripheral speed of the impeller or wheel in feet per second for a given head. Where y = peripheral speed in feet per second. H = heaa water is to be delivered against in feet k=9, coefficient =8 for small pumps and 9*82 for large pumpe. (II.) To find diameter of wheel for a given quanlily oftoater and given head. where D= diameter of wheel in feet # Q Q= quantity of water in cubic D= / —-^r^ feet per minute. V VHxO-16 H=headinfeet 0*16= coefficient (III.) To find revolutions of wheel per minute, tofi-en height of delivery and circumference of wheel are given. ^_ {(8VH)xA:}x60 '*— jjj R= revolutions per minute. ,rT H and Q =same value as above. or R_^^ i= coefficient as in (I.) k in this case being = 158 for small pumps and 187 for large pumps. (IV.) To find effective horse-poicer required, given gallons per minute, for a given quantity of water to be delivered against a given head. E.H.P. =ert'ective horse power. gjT p _Gx lOx Hx -66 G= gallons to be delivered |>er * ' ' 33,000 minute. H ^same value as above. (V.) To find diameter of suction and delivery pipes in inches. __ - f/ = diameter of pipe in inches. a - '22b ^fg y = gallons delivered per minute. Sinkiiig Pump. — During sinking operations an arrangement of pumps is required differing from that in use imder ordinary circum- stances. A common arrangement in sinking is a * sliding suction' pump working through a * packing gland.' It may be lowered as the sinking proceeds. A short joining piece is used between the sliding suction and the working barrel, this short piece being made of weaker metal than the other parts, so that in case of a side stroke from a shot it may give way, without injuring the more expensive parts. The method of operating is usually to iix all the pipes above the working barrel with collaring, and to allow the working barrel and sliding piece to be lowered as sinking proceeds. The sliding piece is generally made the length of one of the pipes, so that when it has been let out this distance, the column is *cut' above the working l)arrel and another length added, when the pumping may proceed as before. The objection to this method is, that the pipe column requires to bo cut at intervals, say 9 ft., as the sinking pro- ceeds ; but if the pumps are not large it works very satisfactoiily. 340 PEACTICAL COAL-MTNING. For light pumpe a strong flexible hoee maj be used instead of the eliding suction. The pump rods are usually longer than the column of pipes, and short pieces are uaed as lengthening parts, or an arrange- ment with a gland fixed to the bell-crank, and the rods clamped to it, is used. This is more satisfactory, as the rods can then be put in the full length and lengthened as sinking proceeds. The second method of employing a sink- ing pump is to lower the whole column, either with iron rods and screws, or by ropes worked from a steam winch at the surface, ' as the work proceeds. A combination of both of these methods is possibly the best and safest. Fig. 403 shows the arrange- ment of lowering a sinking set with ropes and ground spears. The pipe column a is fixed rigidly to the suction piece b, and between the suction piece and the clack piece a short pipe A is inserted, having extra broad and strong flanges. Immedi- al«ly below the flanges, two strong iron glands c e are fixed and conncct«d to the ' grotnid spears ' d d; at the top of these spears are two sheaves e e, connected to the spears with strapping plates. At the surface two similar sheaves // are fixed, ^ round which the ropes 1/ g work. They are operated by a steam winch at the surface, so that the whole lift can be lowered as sinking proceeo lower lift being flooded by a sudden inflow. Where piimpa are operated with rods in the shaft, it is Flas. 405, 406, 407.— Doubl* jilaogsr jiump. almost an invariable custom at coal mines to work the rods with a pair of bell-cranks, unless tliey are worked by a diroctr-acting engine, such as a Bull engine. By using double bell-onuiks the power is more 346 PRACTICAL COAL-MINING. evenly distributed, and where a number of lifts have to be operated, fewer offsets are required than if the pumps were all worked off a single bell-crank. Figs. 406, 407 show front and side elevations of a good arrangement for working two or more lifts by a pair of bell-cranks. The features which commend this arrangement are that the pump is a double-acting one, and that there are two distinct sets of rods carried down from the surface, the lower lift in each case being worked by a cross-head on the rods of the lift above. When the sets are large, ue, above 20 in. diameter, it is often a difficult matter to fix on a suitable arrangement to occupy as little space as possible. Figs. 405, 406, 407 show a plan, elevation, and side elevation, respectively, of a very compact arrangement for a double plunger set of 24 in. diameter, with one central delivery column common to both pumps. In this disposition of the pumps as little space as possible is taken up, and it is in every way convenient. The foundations for the pumps are generally strong beams of timber built into the shaft, or wix)ught-iron or steel girders, the latter being much to be preferred, as they give the maximum of strength with a minimum of space, and are less liable to decay than timber supports. A few worked-out examples on pumping, such as are often set at examinations, are given below, in the hope that they may prove useful. Question. — How many strokes per minute can be made by the piston of a pump whose area is 2 sq. ft., length of stroke 5 ft., and the height to which the water is raised 60 fms., driven by an engine of 80 horse-power ? H.P. x38000 = AxLx62-6x(ixa^ When H.P. = horse power, A = area of pump in sq. ft., L= length of stroke in feet, 62 '6 = number of lbs. in 1 cub. ft. of water, <£=: height in feet water is raised, 26= the number of strokes required per minute. . '. 80 X 33000 = 2 X 5 x 62'5 x 360 x .<; after cancelling 880 = 75* . •. a; = ?^ = 11 -86. Quesium. — At what rate will it be necessary to work a pump 12 in. diameter with 4^ ft. stroke, to deal with 200 gallons of water per minute in a shaft 200 yds. deep, and what is the approximate horse- power required 1 Using the same letters as above, and G= gallons of water per minute, and D = diameter of pump in inches, 6 *25 = number of gallons in 1 cud. ft. Allowing 10 per cent of loss for slip, G = 200 4- 20 = 220. r, 6"26 X D* X 7854 X L X as i i .^ v • vis j 6*25 x '7854 .'. G= ~^-. , or calculation can be simplified, as ■ 114 144 = •034 .'. G = D'x •034xLxa! 220 = 12'* X •034x4*5 XX 220-22*03 X 220 x= =9*16 strokes per minute. 22-03 ^ • • PUMPING. 347 As 1 gallon of water is equal to 10 lbs. . '. H.P. x 33000 = 220 x 10 x 200 x 8 10 X 2' 83000 «. w D 220 X 10 X 200 X 8 .^ or a, r . = ■_._■_ = 40 Question. — A hydraulic pump having au 8-in. diameter plunger is wrought by means of a head of water brought from the surface in pipes 2 in diameter. Find the total pressure on plunger and weight of water in pipes, if the depth of the shaft is 360 ft. r»- ' ^u •jii.jfi. rfx 12x62*5 12x62*5 Pressure in lbs. per sq. m. due to head of water = — — — , or as — 1728 1728 =%'434 .*. pressure in lbs. per sq. in. due to head of water =(£x *484=860x '434 = 156-24 lbs. Total pressure on plunger = area of plunger in sq. in. x pressure in lbs. per sq. in. =8« X -7864 X 156 •24=7852-62 lbs. «r • 1.1. r * • • f =156*24 x2x -7854 Weight of water m pipes | ^490.51 ly^ Question. — What number of gallons and cubic feet of water can be pumped per hour from a pit 600 feet deep, by an engine of 200 H.P., assuming the efl&ciency of the engine to be "6 ? Let X = weight of water in lbs. raised per hour. Thena:xd=H.P. x33000x60x 6 as X 600 = 200 x 83000 x 60 x '6 200 X 83000 X 60 x '6 600 = 396000 lbs. 1 gallon of water =10 lbs. .*. gallons per hour=~ -=39600 1 cub. ft. of water =62*5 lbs. .*. cub. ft. per hour= *[ , =6886 '^ 62*5 Question. — Find the quantity of water delivered by a double-acting plunger pump, if the plunger is 7 m. in diameter, length of stroke 4| ft., and working at 20 strokes per minute. Also find the horse-power if the shaft be 90 fms. deep. Using the same notation as in Question 2, and also let N = number of strokes of plunger per minute. Then G = D« x -034 x L x 2 x N =7'x *034 X 4*5 X 2 X 20 =299*88 gallons per minute. H.P. X 33000=0 X 10 xd H. P. X 33000 = 299*88 x 10 x 90 x 6. After cancelling H.P.=??^^=49*07. Question, — Give the principal sizes of a direct-acting pumping engine fitted with a fly-wheel which you would erect to raise 400 gallons of water per minute from a depth of 80 fms. ; allowing } for stoppages, I for efficiency of engine, and 10 per cent, for slip of pumps. 348 . PRACTICAL COAL-MINING. As ^ has to be allowed for stoppages, and 10 per cent, for slip of pumps, . •. Gallons to be raised per minute = — -^ — + 10 per cent =660. We would therefore require to provide a pump capable of raising 660 gallons per minute. Assume the speed of the pump to be 100 ft. per minute. G=I>'x -034 X speed or D=v/«'^^,^ ^' "'r''-\/ ho.^^ = 13g, or 14 in. approximately as V -031 X speed V 034x100 ' *' ^ the diameter of pump required. Then to calculate size of engine required to raise 600 gallons per minute, we may equate the work thus : — Work done by engines work done in shaft ; or D^ X 7854 x P x speed x £= weight of water in lbs. per minute x height to be raised in feet Where £= efficiency of engine =§ or '66. If we assume the effective steam pressure to be 50 lbs. per sq. in., and the speed of engine to be the same as the pump, 100 ft. per minute, Then D^ x 7864 x 60 x 100 x "66 = 600 x 10 x 80 x 6, after cancelling '08689 D3=96 / 96 and D = >v/ -rrr^nr^ = 38 8 in. diameter of cylinder. V -08639 ^ -08639 The engine is to be direct-acting, so that it could have a 5 ft. stroke, and nin at the rate of ten double strokes per minute ; the diameter of cylinder being 33 in., and the steam pressure 50 lbs. per square in. Suppose the above engine to be compoimd and working expansively, and the steam to be cut off at ^ of the stroke ; what would the diameter of the low-pressure cylinder require to be ? The size of the low-pressure cylinder may be found by the formula: a= — = : Where a = area in sq. in. of high-pressure cylinder VE A= ,, ,, low „ ,, p E = number of expansions of steam in cylinder =~ P=mean effective steam pressure in lbs. per sq. in. T = terminal pressure of steam = P -1 I = length of stroke before steam is cut off ^= I. II after „ „ PUMPING. 349 Here T=60x^? = 16-6 lbs., and E = ,4^^ = 3, and by formula a=A,or if we let £{= diameter of high pressure cylinder andD= „ low „ „ thenrf'x'7854 = P'^'7J^^ VE . '. D« X -7854 = d» X '7854 x VE r. /SS'-* x -7854 x V8 V .7854 = V1883 97 = 43 -4 in. If we allow the same efficiency for this cylinder as for the high- pressure one, then its diameter would require to be 43*4 + J = 57 "8 in. The ratio between the two cylinders is often taken as 1 : 1 "6 or 1*5 when the number of expansions is less than 10. GHAPTEB Xni. VENTILATION. Chises Present in Mines. — The principal causes of impure air iu mines are : — The exhalations, of men and animals ; burning lamps or candles ; gases given off naturally from the strata and those resulting from blasting; decaying timber in the workings; absorption of oxygen by chemical agencies ; introduction of foreign substances. In breathing, oxygen is withdrawn from the air and CO^ is given off, together with a certain percentage of nitrogen ; a man working for eight hours will give off, on an average, over 5 cub. ft. of COg. The quantity of air inhaled by a man is said to be *42 to '45 cub. ft. per minute, or 25*2 to 27 cub. ft. per hour when at rest ; but in a mine it will require much more than this to keep the air pure, possibly 100 to 120 cub. ft. per minute in a non -fiery mine, and in fiery mines, where much gas is given off, 300 to 400 cub. ft. per minute, while every horse in the mine will require three to six times as much air as a man. The quantity of air supplied to a colliery should bear some ratio to the amount of coal raised per shift, because the more actively the working proceeds the greater will be the amount of gas liberated. In non-fiery pits 80 to 100 cub. ft. of air per minute per ton of coal raised should suffice, and 100 to 200 cub. ft. per minute per ton of coal raised in fiery collieries. No hard and fast line can be drawn that will suit every case. Burning lamps or candles also absorb the oxygen from the air and give off deleterious gases, principally COg and small quantities of CO. Fire-damp and choke-damp are given off more or less freely in nearly all mines, and are often the principal causes of impure air in the workings. Timber in some mines, especially in return airways, decays very rapidly and pollutes the atmosphere. To prevent this as much as possible, the l)ark should be peeled off and the timber thoroughly seasoned before being used underground. Chemical agencies, such as the action of water on iron pyrites or other ferruginous minerals, absorb considerable quantities of oxygen, VENTILATION. 351 and give off H2S. The coal itself absorbs the oxygen of the air to such an extent as sometimes to ignite spontaneously. The introduction of foreign substances into the air takes place on blasting by explosives, the gases naturally given off from the coal and fine coal-dust held in suspension, produced by breaking down the coal, or carried down into the workings with the intake air-current from the screens on the surface. The statement by manufacturers that explosives cause no fumes is wrong, as nearly all explosives give off CO and COg in varying quantities, and also a considerable amount of solid residue. The smoke of gunpowder is largely composed of fine particles of carbonate and sulphide of potassium. Dynamite, when exploded, sends into the air, in a finely divided state, the 25 per cent, of infusorial earth which it contains. Boring shot-holes either in the rock or coal also sets in motion considerable quantities of fine dust which help to pollute the air. From these causes, the atmosphere in the workings is very soon rendered impure and dangerous to breathe, unless means are adopted to clear them, and keep men and animals supplied with pure air. The only safe and practical method is to keep up a current of air of sufficient quantity and velocity as to carry off the deleterious gases as soon as formed. As the symbols, specific gravities, and atomic or relative weights of the gases met with in mines are frequently referred to, it will be as well to commence by defining these terms. The Specific Gravity or Density of a body is the ratio of the quantity of matter contained in a given volume to the quantity of matter contained in an equal volume of a substance chosen as a standard. Air is nearly always the standard adopted when com- paring the specific gravity of gases. 77i« Atomic WeigM is the lowest proportion by weight of an element which can combine chemically with one part, by weight, of hydrogen. Symbols, — The chemist divides all substances into elements, com- pounds, and mixtures. Of the former there are between 60 and 70, and for the sake of convenience and brevity in referring to them, the first letter only, or two distinctive letters of the names, are used. Thus H is the symbol for hydrogen, 0 for oxygen, etc., etc. Gases are divided into three classes, viz., elementary or simple gases, compound gases, mechanical mixtures. An elementary or simple gas consists of one element only, i.e. of a substance which it is impossible to split up or divide. Compound gases are composed of two or more elements chemically combined with each other. This combination results in the pro- duction of a gas differing in its properties from either of the elements of which it is composed. Mechanical mixture takes place when two or more substances or elements are brought together and no chemical action results. The 352 PRACTICAL COAL-MINING. atmosphere of a mine is a mechanical mixture of air and the various gases and emanations described above. The elementary or simple substances of which the compound gases found in mines are composed, are — Hydrogen, H ; Oxygen, O ; Nitrogen, N ; Carbon, C ; Sulphur, S. Hydrogen, — Symbol, H; atomic weight, 1 ; density 0-0693 (air = 1). An inflanunable gas; possessing, when pure, neither colour, taste, nor smell ; and a non-supporter of combustion or life. The fact may here be noted that all inflammable gases are non-supporters of combustion in the ordinary sense. Hydrogen being the lightest substance known, it is usually taken as the standard of atomic weight, the weight of all other gases being expressed in terms of hydrogen as unity. 1000 cub. ft. of hydrogen at 14*7 lbs. (atmos- pheric) pressure per sq. in., and at a temperature of 32** F., weigh 5-606 lbs. Oxygen, — Symbol, 0 ; atomic weight, 16. Oxygen occurs in the free state in the atmosphere, mechanically mixed with about four times its volume of the inert gas, nitrogen, which acts as a diluent to the highly active oxygen. Oxygen has neither colour, taste, nor smell ; does not bum in air, but is the great supporter of combustion and life. All forms of burning, breathing, decay, etc., are simply manifestations of the combination of various substances with oxygen. Since 1000 cub. ft. of hydrogen weigh 5-606 lbs., 1000 cub. ft. of oxygen = 5-606 x 16 = 89-69 lbs. Nitrogen, — Symbol, N ; atomic weight, 14 ; non-inflammable gas ; no colour, taste, or smell, and does not support combustion. It forms f ths by volume of the atmosphere, but is altogether a very inert gas, being very inactive in all its qualities under ordinary conditions. While not actively poisonous, it is incapable of supporting life. 1000 cub. ft. of nitrogen = 5-606 x 14 = 78-48 lbs. Carbon, — Symbol, C ; atomic weight, 12. Carbon is not a gas, and it is never foynd free in a gaseous form like hydrogen or oxygen. Charcoal, coke, graphite, and the diamond are all forms of carbon, the diamond being the purest. This element is often present in com- pound gases, and, from their properties, gaseous carbon is assumed to have no colour, taste, or smell, to be inflammable, but a non- supporter of combustion. Sulphur, — Symbol, S ; atomic weight, 32. Sulphur is also a solid element at ordinary temperatures ; at higher temperatures it becomes a liquid with a clear amber colour, which on continuous heating becomes darker, and at a temperature of 840^ F. it becomes a dense red vapour which is combustible, and a non-supporter of combustion and life, without smell itself, but with a strong pungent smeU if allowed to combine with oxygen or with hydrogen. Its combination with oxygen constitutes its chief claim to importance as regards mine gases. The only naturally occurring mechanical mixture we have to deal VENTILATION. 353 with in mine gases is air, which cannot be correctly expressed by any formula. Air is composed approximately of 4 volumes of nitrogen and 1 volume of oxygen, 14*43 being its relative weight as compared with hydrogen. In addition to these two gases air also contains several other constituents, such as carbonic acid gas or choke-damp, water vapour, and argorij a constituent recently discovered by Lord Rayleigh. The proportion of carbonic acid gas (COg) in the air is about 77jnr^^ P*^ ^^ ^^® whole volume, or varies jfrom 2 to 10 vols, in 10,000 vols, of air. The average composition of normal air is : — Yolumes per 1000. Nitrogen, ...... 779*0600 Oxygen, Aqueous vapour, Carbon dioxide, Ammonia, Ozone, . Nitric acid, 206*5940 14-0000 *8360 •0080 •0016 •0006 1000-0000 The average amount of COg present in the air is '04 per cent. ; in ordinary mines, 0*78 per cent. ; and in badly-ventilated mines, 2-73 per cent. As a continual supply of COg is being given off from many sources^ it is necessary to have some provision made to keep down the amount present in the atmosphere. Nature itself makes the necessary provision. Plants inhale the CO^ present with the absorp- tion of the carbon and some of the oxygen, the compoimd retained being assimilated, and helping to build up the plant tissue. Moisture in the Air. — There is always a certain amount of water vapour present in the atmosphere, but the quantity is subject to great variation. The barometer gives indications as to the condition of the atmosphere in this respect. The amount of vapour or moisture which the air can take up depends on its temperature : the higher the temperature the more water can be held in suspension. There is, for any given temperature and pressure, a maximum amount of moisture which a given volume of air is capable of taking up, and at which it is * saturated.' The following quantities of water correspond to * saturation ' for the temperatures given : — Degrees F. Weight of water in lbs. 1000 cubic feet of air at 32*' contain 0-808 lb. 1 M 50' ,, 0-667 „ l« |« Oo ff < 1-066 „ )t t) 86 ,, 1-873 „ When air saturated with vapour is cooled, the moisture is condensed and falls in the form of rain or dew. The relative weight of water vapour to air is as 9 to 14}. Water vapour is therefore much lighter than air, and a column of moist air 23 354 PRACTICAL COAL-MINING. is much lighter than a column of dry air of the same height. When the barometer falls it indicates a decrease in local pressure, because the air is moist and there is a probability of rain, whilst when the barometer is high it indicates that the air is dry and that dry weather will occur.* The amount of vapour in the air can be ascertained from tables published for the purpose (the physical tables edited by Prof. Guyot, of Washington, are the best), giving the average saturation for different temperatures. But probably the best means of dealing with this is to find by means of calcium chloride tubes carefully weighed before and after a known volume of air has been passed through them ; the amount of moisture present in the intake and also in the return can be thus ascertained, and the difference between these two quantities will be the amount of moisture absorbed from the underground workings. The amount of moisture in the air can also be ascertained by finding the dew point, for the intake and return currents, by means of a hygrometer. Example.— A ventilatinff current of air of 150,000 cub. ft per minute saturated with vapour passes down the down-cast shaft at a temperature of 32*" F. When it leaves the up-cast its temperature is 75' F. and it is still saturated with vapour. Find how much water-vapour this quantity of air has absorbed from the under- ground workings. T + 459 By the formula Qj= — I— - x Qi, the quantity or volume of air in the up-cast shaft = Z5±^^ X 1 50000 ( Qi = quantity of air entering originally. Qq= quantity leaving the shaft T= temperature of %ir in the up-cast t= ,, ,, down-cast 82 + 459 = 1-0875 X 150000 = 163125 cub. ft per minute From the tables already referred to it is found that 1 cub. ft of air at 32** F. contains 2*20 grains of vapour andl „ „ 75^ F. „ 9-41 „ .-. vapour in down-cast volume = ""^ -^^^"=47.10 ib^ {7000 grains =1 lb.} .*. vapour absorbed from mine workings =219*05 -47*10 = 161*95 lbs., or 16*195 gallons of water per minute. The compound gases found in mines are four in number, viz., carbon dioxide (COg), carbon monoxide (CO), sulphuretted hydrogen (HjS), and carburetted hydrogen or methane (CII4). * Height of the Atmosphere. — We are qnite unable to tell to what height the atmosphere really extends, but we can readily estimate its height, from the observed pressure, if we assume it to have a uniform density. The average pressure of the air at the sea-level is 14*7 lbs. per sq. in. at a temperature of 32° F. and 29 '9 in. of mercury. 14*7 X 144»2116'8 lbs. pressure per sq. ft, 1000 cub. ft of air weigha 80*728 lbs. .-. 1 cub. ft =??^= *08072 lbs., and ?^ = 26211 ft =height of air lUOO *vo072 column if the atmosphere were of uniform density throughout VENTILATION. 355 Black-damp, Ohoke-damp, or St3^e, is a gas, or, more correctly, a mixture of gases, frequently met with in mines, especially in old workings or badly ventilated parts of the mine. In fact, in mostly all mines it is generally present to a greater or less extent in the return air currents. Until quite recently black-damp was supposed to be composed of pure carbon dioxide or carbonic acid gas (COj), but the investigations and analyses of Dr John Haldane have shown that this is not the case. In a series of analyses of samples taken from the underground workings of several collieries it has been shown that the composition of black-damp was very regular, and con- sisted of 85 to 88 per cent, of nitrogen and 12 to 15 per cent, of carbon dioxide. The following table, taken from Dr Haldane's pub- lished researches, will show more clearly the composition of this gas : — Table showing the Composition and Specific Gravity of Black-damp. Component Gases. I. 1-46 82*56 10*64 5*35 II. 0*72 80-78 11-03 7-47 III. IV. V. VI. I r Oxygen, . Composition of 1 Nitrogen, the sample | Carbon dioxide, 1 \ Marsh gas, Calculated specific gravity of sample, 10-07 82*80 7 63 0*00 100*00 9-60 83*08 7*82 0*00 100-00 13-66. 78-97 4*49 2-88 100 00 18-60 80*68 4-82 0-90 100-00 100-00 100 00 1-0106 1 0080 1*0274 85-30 14-70 100*00 1 -0268 1 -0029 85-86 14-14 100*00 1-0129 85*90 14-10 Calculated com- 1 Nitrogen, . 87 '87 position of the /..^uA^iL*;^- To.ii pureblack-damp \ ^•^^^ ^*°**^"' ^2*^^ 87*66 , 12*3r> 86*48 13*52 100-00 1 100*00 . 100*00 100-00 Calculated specific gravity of the pure black-damp 1-0890 1-0403 10534 1 -0468 1 -0502 1-0500 It will be seen that the specific gravity of blaek-darap is very much lower than was hitherto suppc^ed to be the case. The specific gravity was usually taken at 1-52 (air=l), which is the density of pure carbon dioxide, whereas it is now shown to vary from 1 '0390 to 1 0534, or only about 4 or 5 per cent, higher than air. Black- damp as actually met with in mines may, moreover, be sometimes lighter than air, in consequence of admixture with fire-damp. Black-damp is produced by the decomposition or combustion of carbonaceous matter in a free supply of oxygen, and is formed in mines by the decay of organic matter, by the exhalations of men and animals, the gaseous products resulting from burning lamps and blasting operations — in fact, wherever combustion is going on. In some mines it is abundant, and is given off naturally from the strata like fire-damp. 356 PRACTICAL COAL-MINING. According to Dr Haldaue, the two principal theories which may be advanced to account for the presence of this gas in mines are — (a) that the formation of black-damp is due to the oxidation of coal or associated strata ; (b) that it is evolved from the coal or associated strata. He regards the first — the oxidation of coal — as being the principal and most likely cause of the origin of black-damp in coal mines. It is well known that many kinds of coal when exposed to air undergo a slow process of oxidation ; in fact, the oxidation may pro- ceed so rapidly as to give rise to a considerable increase in the temperature and finally to spontaneous combustion, causing what are known as gob fires. He maintains that black-damp is nothing but the residual gas left by this slow process of oxidation of the coal, at ordinary temperatures. Black-damp does not issue at high pressure from freshly-cut coal in the same way as fire-damp ; and coal which lias had ample time to drain off all its other gases, may still continue for months and years to produce black-damp. On the other hand, the gas is frequently met with in metalliferous mines and in fire clay, lime- stone, ironstone, and other measures where no coal seams are present. Black-damp has neither colour, taste, nor smell, except when pre- sent in large quantities, when a slightly acid taste is experienced. This would, however, be no guide to its detection in mines. It docs not buni, nor does it support combustion or respiration. It can l)e easily detected, as when lights are lowered into it they become black and smoky, or are extinguished. Another test is to pass a quantity of the suspected air through lime-water, when, if the gas is present, the water will turn milky. The proportion of black-damp in air required to extinguish the flame of a lamp varies according to the percentage of oxygen present. Professor Clowes states that it requires tlie presence of 15 per cent, of black-damp in the air to extinguish a flame, while Dr Haldanc gives the percentage re(iuired for the extinction of a flame at 15 to 1 9 per cent., according to the kind of light used. The following table gives the result of some of Dr Haldane's experiments on extinctive percentages of black-damp : — Component Gases. Oxygen, . Nitrogen, Carbon dioxide, Marsh gas, Percentage of black-damp, Upright Candle Oil Lamp (bon- neted clanny) Hydrogen Flame Extinguished. Kxtinguished. Extinguished. 16-43 249 1-8S 100 00 11*41 79 53 5-37 3-69 100-00 19 -56 41-72 VENTILATION. 357 Black-damp is always difficult to deal with, especially in the case of dip workings, as it may settle near the floor, and a current of air passing over it may fail to remove it. Its presence should always be suspected in such workings (especially if old and unventilated), and at the bottom of wells and sumps. It may be removed from sumps by lowering a bucket containing quicklime, which absorbs large quantities of COg, or by letting a quantity of water fall down the shaft, thus producmg a strong current of air to displace it. The latter method can only be adopted when there is plenty of pumping power available to raise the water to the surface again. Carbonic Oxide, Carbon Monoxide, or WMte-damp. —Composition, CO ; atomic volume, 14. This gas is also colourless and tasteless ; but sometimes possesses a sweet and delicate odour, especially when present in large quantities. It is a combustible gas, burning in air with a characteristic blue flame and forming carbon dioxide, and is a non-supporter of combustion. Fortunately this gas is found only in exceptional circumstances, such as underground fires, etc. Carbonic oxide is formed by the combustion of carbon with a deficiency of oxygen, or, briefly, is the result of incomplete combustion. Small quantities of this gas are also given ofl* on the explosion of gunpowder. It is usually a constituent of after-damp, and it is said to be given ofl* naturally in some metalliferous mines, and has been found in tunnels during driving operations. Although this gas is inflammable, it cannot be detected by the flame of a lamp until there is about 12 per cent, present in air, whereas much smaller quantities are fatal to life. Carbon monoxide is an extremely poisonous gas; very small quantities present in the air rapidly give rise to severe headache and giddiness, with palpitation of the heart, and if breathed for any length of time, insensibility and death quickly follow. It has been proved that as a very small percentage of this gas affbcts small warm- blooded animals more rapidly than man, mice or small birds should be utilised in the detection of this gas, the mouse or bird being carried in a small cage, or inside the gauze of a safety lamp. If on entering the foul atmosphere the animal becomes incapable of motion, it should be regarded as a sign of real danger. It should be re- membered that while an atmosphere containing I per cent, of CO would be almost immediately fatal if breathed, a very much smaller percentage would be equally fatal if breathed for a sufficient length of time; 0*5 per cent, will saturate the blood as well as I per cent., but with the lower percentage it will take a much longer time for saturation to be completed. With about 0*06 per cent, of CO in the air, the blood of a man becomes 30 per cent, saturated after I^ hours. O'l per cent, will give 50 per cent, saturation ; with 0*2 per cent, the saturation point is increased to 67 per cent., which would soon bring about unconsciousness and death. With I per cent, of CO in the air, saturation of the blood wotdd take place in five or six minutes, and death would rapidly supervene. 358 PRACTICAL COAL-MINING. The main thing for the student to remember is that the small pro- portion of CO necessary to produce a fatal result cannot be detected by the flame of a lamp, since a flame cap will not form until there is considerably over 1 per cent, present. If a person is suffering from carbon monoxide poisoning, pure oxygen should be administered, stimulants given to act on the heart and stomach, and the victim wrapped in warm blankets, and hot water bottles applied. Bringing any one sufiering from the effects of this gas suddenly into the fresh air may prove very dangerous, and even may prove fatal. Why this occurs has never been satisfactorily explained, but still it is a fact which has been noted in the case of several colliery accidents. Sulphuretted Hydrogen. — Composition, HgS ; atomic volume, 17. This is a combustible gas burning with a deep blue flame, producing sulphur dioxide (SOg) and water; does not support combustion, and has no colour, no taste, but a very strong odour of rotten eggs. Like carbonic oxide, this gas is never found in large quantities in mines. It is produced by the decomposition of pyrites by water. It is an exceedingly poisonous gas, a very small per- centage causing sickness and giddiness. It is never a source of great danger in coal mines, as its presence, even in small quantities, is easily detected, owing to its strong smell. Sudden outbursts of this gas have been known to occur, however, in copper and salt mines, causing loss of life. Carburetted Hydrogen, Methane, or Marsh Gas, is known amongst miners as * fire-damp, ' * fire, * or * gas. ' Composition, CH^ ; atomic volume, 8. Fire-damp is a gas with neither colour, taste, nor smell. It is highly inflammable, and a non-supporter of combustion. Carburetted hydrogen is found in petroleum, and is given off when the oil is taken out of the earth and the pressure removed. It is also found in marshes (hence the name marsh gas) as the result of the decay of vegetable matter. Vegetable matter is principally composed of carbon, hydrogen, and oxygen, and when it undergoes decomposition in the air, in a free supply of oxygen, the final products formed are carbon dioxide (COj) and water (HgO). When the decomposi- tion process takes place fcWiout access of oxygen, such as under wat«r, carburetted hydrogen (CH^), which is a reduction product, is formed. This explains why this gas is held in the coal and given ofi* naturally when the mineral is worked. The association with carburetted hydrogen of free hydrogen, oxygen, nitrogen, and also heavy hydrocarbons, is said to be due to different stages of carbonisa- tion of the vegetable matter, or it may have been produced by the simultaneous decomposition of animal matter. Blowent, — As the formation of coal must have proceeded under a complete covering of layers of mud, sand, etc., it is evident that the gaseous products accompanying these changes must have collected and then filled, under considerable pressure, not only joints and fissures in VENTILATION. 359 the seam and surrounding rocks, but must have permeated the coal itself. The hissing and crackling noise observed at the face of freshly-worked coal shows that the occluded gases are held under a certain pressure. Where the pressure is great the gas issues from the coal with a hissing noise, like that of steam escaping, a vent of this description being called a * blower.' These blowers often continue for lengthened periods to give off fire-damp, showing that they must communicate with reservoirs of gas. The pressuie has at times been measured, and in some places pressures varying from 460 to 900 lbs. per sq. in. have been recorded. Where gas at these enormous pressures is present, liability to sudden outbursts always exists. Such outbursts are very dangerous, both by their fouling the air currents and dislodging material. In the black vein seam of the South Wales coal-field large cavities filled with fire-damp are met with, and when the seam is being worked they sometimes burst out imexpectedly, forcing out large masses of coal and dust, and resulting at times in loss of life. Outbursts also occur from the floor of seams in such large volumes and with such suddenness as to foul the air to a dangerous degree and cause serious explosions. When faults are being approached, blowers of fire-damp are not infrequently liberated, being sometimes preceded by an out- flow of water. Great care should therefore be taken when working in such circumstances. In some shallow mines fire-damp is seldom met with, or found only in very small quantities, having probably escaped from such mines through the permeable strata to the surface. In some seams it is, on the other hand, given off in very large quantities, especially from those earliest worked, which usually drain off the gas from the other seams. Generally, fire-damp is most abundant in seams of considerable depth, being given off naturally from the strata, and also freely from the coal face ; it also issues from cracks in the roof and floor, large volumes being given off at times, sometimes heaving up the floor or causing falls of the roof. Carburetted hydrogen is rarely found in a pure state. It is generally mixed with other gases, principally carbon dioxide and sulphuretted hydrogen. The small quantities of carbon dioxide found in blowers of fire-damp or in the return air of mines, have apparently little influence on an explosive mixture of carburetted hydrogen and air, according to experiments which have been made with mixtures of fire-damp and air at Bochum and by Kriescher and Winkler at Freiberg, where 5 per cent, of carbon dioxide (COj) was found to have no effect. This is probably also the case as regards other gases associated with fire- damp, such as nitrogen, such gases seeming to act in the same way as an excess of air, merely as a diluent, and tending to reduce the temperature of the explosion. 360 PRACTICAL COAL-MINING. The experiments of Mallard and Le Chatelier, made on behalf of the French Firedamp Commission, show that mixtures of CH^ and air begin to be sharply explosive with 7 per cent, of marsh gas (1 vol. of CH^+12 vols, of air), the maximimi being reached with 10-8 per cent. (1 vol. of CH^ + 8"3 vols, of air), and ceases to be explosive with 14 '5 per cent. (1 : 5 -9). For the inflammability of a mixture of CH^ and air they fix the lowest limit with an amount of 5*8 per cent, of marsh gas, and the upper limit from 16 to 17 per cent. When a mixture of fire-damp and air in certain proportions is brought in contact with a naked flame, combustion may result either in the quiet burning away, or in an explosion of greater or less violence ; that is, in the rapid translation of flame through the whole mixture. In the course of the experiments it was found that whilst 2 vols, of CH^ require for their complete combustion 4 vols, of oxygen, 2 vols, of hydrogen require 1 vol. ; 2 vols, of ethane (CgHg) require 6 vols, of oxygen. Taking the average percentage of oxygen in the air as 20*7 vols., a mixture of air and each one of these gases, to contain sufficient oxygen to bum each completely and form, therefore, the most explosive mixture, must contain the following amounts of each : — Per cent. Pure hydrogen (Hj) .... 29 '28 vols. Marsh gaa (CH4) . . 9*38 „ Ethane (CaHe) . . 5*58 ,, If, therefore, any of those gases be present with CH^, the percentage of such mixed gases required to form with air the most explosive mixture (explosive maximum) will be greater or less than 9 '38, according as the gas is either hydrogen or one of the other hydro- carbons. The following table shows the results obtained by the British Royal Commission on Accidents in Mines, of varying percentages of firedamp on a naked light : — CH4 in air. Effect 2 per cent. . . Produces slight elongation of the flame. 2} ,, . . A distinct elongation. 4| ,, . . Inflames and burns slowly. 6 ,, . . ,, explodes sharply. 0*38 ,, ,, ,, with greatest violence and perfect combustion. 20 ,, The flame lust burns feebly. 25 ,, Extinguisnes the flame. Mallard and Le Chatelier submitted the question of the temperature of ignition of carburetted hydrogen to a very thorough and complete investigation, and have found the temperature of ignition for mixtures of CH^ and air to be 740' C. (1364' Fahr.), and that it is VENTILATION. 361 practically constant whatever be the proportions of the constituents. But it was found that ignition docs not take place immediately the gas, or even a portion of it, has been raised to this temperature ; the gas must be exposed &)me seconds to the above temperature before explosion takes place. Professors Wiillner and Lehmann, in their experiments on the same subject, found that mixtures of CH^ and air in certain proportions were more easily ignited by some kinds of wire, when heated, than by others, copper-wire only causing ignition at the moment of its fusion (about 1100** C), while platinum wire 0*50 mm. diameter ignited at 1480° C. when the mixture was in the proportion of 1 of CH^ to 14 of air. They also found that the most easily ignited mixtures are not the most explosive, viz., 1 : 9 and 1:10, but those containing gas and air in proportion of 1 : 14 (6*6 per cent, of gas). It was also noted that the higher the velocity at which the inflammable mixture was moving, the higher the tempera- ture of ignition. Wiillner and Lehmann also made experiments with electric sparks, and found that open sparks, as produced by an electric current (using a dynamo) between copper wires 3 mm. diameter, ignited mixtures of CH^ and air in the proportion of 1 : 9 with a current of 18 amperes and above, whilst with a current of 15 amperes or less, occasional sparks caused ignition. The ignition took place more easily with brass and iron wires than with copper, but the ignition is no doubt influenced by the heating of the wires, so that a current of 8 amperes may be dangerous. In using carbon points it was found much more difficult to ignite the mixtures than with metal wire ; in fact, an arc of 10 amperes could be maintained in the most explosive mixture without danger. In view of the very large number of mines which now use electricity for some purpose or other underground, it is very desirable that further investigations should be made on this subject. Explosion of Firedamp. — When firedamp explodes with a mixture of air (9*38 per cent. CH^ in pure air), the following reaction takes place: — Before explosion. One volume of CH4 + 20a + ^^2 = or simply CH4 + 40 = CO2 + 2H2O. After explosion. COa +2(H20)+ 16 N blackdamp + steam + free nitrogen. It is very seldom, however, that the exact proportions of fire-damp and air necessary for complete combustion are present when an explosion takes place, as in nearly every explosion the deadly after- damp has been found to contain, in addition to CO2 and free nitrogen, varying percentages of carbon monoxide and free hydrogen. With an excess of CH^, i.e. over 9*38 per cent., the question of resulting pro- ducts when an explosion takes place is a complicated one. There would be incomplete combustion and certainly CO formed, as well as some free hydrogen. Indeed, the reaction would be somewhat similar 362 PRACTICAL COAL-MINING. to that by which generator gas is got by incomplete combustion of coal. Even if a quantitative analysis could be made it would be different with different temperatures, etc. For instance, in the explosion at Micklefield Colliery, April 30, 1896, when sixty lives were lost, it was found on investigation that forty-six of these had been victims to carbon monoxide poisoning, the CO being present in the after-damp, and not to the force of the explosion at all. Dr Haldane gives it as his opinion that on an average about 70 per cent, of the lives lost in large colliery explosions are due to carbon monoxide poisoning. Means of Detection, — Fire-damp is usually detected by means of a *Davy' lamp, or by one of the other numerous safety lamps now used. To detect this gas the flame should be turned down as low as possible in the lamp, because, if there is a large flame, it is impossible to see the * blue cap ' which forms on the top of the flame if fire- damp is present. The ' cap ' increases in length as the proportion of gas increases, until, when there is 6 J per cent, present, the *blue cap' fills the gauze of the lamp. With this percentage of gas the mixture would be moderately explosive, the violence of the explosion becoming greater as the percentage of gas in the air increases, imtil it reaches 9*38 per cent., which is the most explosive point. None but experienced men ought to be allowed to act as firemen and examine for gas in underground workings. In collieries where gas has not been detected for twelve months, the examination of the workings may be made witli an open light, but this is a practice which ought not to be allowed, as gas may appear at any time. The practice of allowing a fireman to take down a naked light along with his safety lamp, on the understanding that the naked light has not to bo carried beyond a certain point, is a practice that cannot be too strongly condemned, and no manager of a colliery ought to allow such a thing, as many accidents have resulted in the fireman making an improper use of the open lamp and carrying it where it ought not to be. Fire-damp may accumulate in large quantities in the open waste, where pillars arc being taken out, and in rise workings or in holes in the roof, because, being very much lighter than air, it seeks the highest point in the workings. If the seam worked has a soft shale roof and a bed of hard rock, or fakes above, as in fig. 408, the soft shale falls at once, when a * lift ' has been taken off the pillar and the wood first drawn, but the rock does not break for some time after- wards. This causes an open space to be left between the fallen shale and the rock, in which fire-damp accumulates, if present, so that when the rock ultimately falls the space is filled up, and the gas is forced down the edge of the waste into the working places, and, if naked lights are used, may cause an explosion. The only method of dealing with this danger is to work with safety lamps. TKNTILATIOH. 363 If the Longwall aystem of working ia adopted, there may he a space formed hetween the ahale and the rock, which contains gas that escapes into the workings, owing to a subsidence of the rock. To obviate this, it is common to rip one place up to tho rock, the road of course being banked up ; this road, which, it possible. Fio. «OS.—Gu-mted cavity. should be the return airway, has now direct communication with any space that may exist, and consequently acts as a drain for the gas. In sinking shafts, sudden outbursts of lire-damp have often occurred. When approaching a coal seam the strata arc often displaced for a considerable distance from the seam, allowing the gas to issue into the shaft (fig. 409). This may take place more readily after a number of shots ,, ' have been fired, and therefore great ''',-. care should be taken in such cases ^\S to examine the shaft with a safety ~ lamp bcfoi-e proceeding with tho '.ij work. The danger may also be ^r^ * 'JT-^ guarded against by putting a bore- ' ~'' hole to the coal-head 12 or 18 ft. in advance of the sinking. Another danger lies in pumping water from old workings or disused shafts whore gas may be confined, as when the water pressure is lowered ^'^'M to a certain point the pressnre of — ^.-"' 1-^. r^^ ^-^^~~ gas may exceed it, and rush out, with pm. io9.-Gm vent, or ' blower.' dangerous consequences if any naked light be near. A case of this kind occurred at Kinniel Colliery, Bo'ness, a few years ago, whereby two men lost their lives. Systems of Ventilation. — Tho different methods of accomplishing ventilation arc :■ — Natural ventilation, waterfalls, furnace or steam jets, feci procii ting or displacement machines and fans. We have seen that air possesses weight; 459 cub. ft. of air at 364 PRACTICAL COAL-MINING. 0** F., and 1 iu. barometric pressure, weigh 1*3253 lbs. It is there- fore forced along a level road or to the dip more easily than to the rise workings, and this is well known in practice, for with airways of equal area a greater proportion of air will find its way to dip workings. Since air has weight it possesses the property of inertia, which is the resistance offered by a body to any force tending either to impart motion to it or to influence it when in motion. Wlum two shafts are sunk and connected by a passage, and tfte density {weight) of air in the two shafts is equal, no current of air foill circulate, no matter what fJieir respective sizes may be.* If, however, one column of air has a greater density than the other, then the heavier coliunn will overbalance the lighter one and set a current in circulation. To cause a current of air to circulate, some means must be adopted to alter the density of one of the air-columns. This may be done in three different ways, viz., by expansion in the up-cast ; compression in the down-cast ; exhausting the air from the up-cast. Expansion of the air in the up-cast may be attained by natui'al ventilation, furnace, or steam jet. Compression in the down-cast may be procured by means of a waterfall or by compressing fans. Exhausting the air from the up cast may be carried out by displacement machines or by exhau»t fans, the latter being the commonest means employed at mines. Natural Ventilation. — A mine communicating with the surface by two distinct shafts, having air circulating in them without arti- ficial means, is said to be naturally ventilated. The ventilating current thus set up is caused by a difference in pressure between the two shafts, itself the result of a difference of temperature. Therefore, to have a current of air circulating naturally, there must be a differ- ence in depth between the two shafts, to secure a difference in temperature and pressure. At a short distance below the surface of the earth — 50 to 60 ft. — a point is reached where the temperature is constant throughout the year, and as the air acquires nearly the same temperature as the strata, it also is nearly uniform throughout the year. Descending from this point, the temperature increases on an average 1** F. for every additional 60 ft., and in the case of a mine with two shafts of different depths, it follows that there will be a tendency for a current of air to circulate between them. The air, in travelling round the workings, will also get heat imparted to it by the burning of lamps and the natural heat given off from the strata. Natural ventilation may therefore be due to a difference fn depth of the two shafts, due to a difference in surface level, or a difference in depth due to the inclination of the seam. • Coal Mining, by II. W. Hughes, 1899. VENTILATION. 365 Suppose there are two shafts, one 20 fms. in depth and the other 100 fms., the difference in depth being due to difference of surface level. In the winter time, with the temperature at freez- ing point on the surface, at the bottom of the shallow shaft the temperature would be 52 ** F., and at the bottom of the deep shaft it would be 59' F. Now there is a difference in the depth of the two shafts of 80 fms., which would represent a column of air of that height above the surface level at 32* F., opposing a like colunm of the same height in the deeper shaft at a very much higher temperature, and therefore very much lighter. Let us now examine the pressure exerted in both shafts; the shallow shaft would, of course, be the down-cast in winter, and the deep one the up-cast ; the pressure in the down- cast would be — 480 ft. at 32° F. and 1 cub. ft. of air at 82** F, = -081 1 lb. . •. 480 x -0811 = 38-92 lbs, 60 „ 60'F. „ 1 „ „ 50' F. = -0780 lb. . •. 60 x -0780= 4*68 „ ♦120 „ 62'F. „ 1 „ „ 62'F. = -0778lb..'. 120 X -0778= 9-83 „ Total for down-cast =62 -98 „ in the up-cast shaft the pressure would be 60 ft. ut 32" F. and 1 cub. ft. of air at 82" F. = '0780 lb. . '. 60 x '0780 = 4 '68 lbs. 640 „ 69" F. „ 1 „ „ 69"F.--0767 „ .-.540 X •0797 = 41-41 „ Total for up-cast =46 09 „ The difference of pressure causing the current to circulate will be 52-83 - 46-09 = 6-84 lbs. in favour of the shallow shaft, which will cause it to be the down-cast in winter ; while if we examined the case in the same manner in summer, it would be found that the deep shaft would then have become the down-cast. The weight of a cubic foot of air at any temperature and height of barometer may be found by the formula W = — ^ ^-^r— ^ ^ ^ + 459 Where W= weight of 1 cub. ft. of air at the given temperature. B » height of barometer in inches. <= temperature of air in degrees Fahrenheit 459 = CO- efficient of expansion. 1*3253 = a constant (459 cub. ft. of air at 0' F. and 1 in. bar. press, weighs 1*3253 lbs., and 459 cub. ft. of air at 0° F. and B inches of barometric press. = 1*3253 x B). The more nearly the two shafts approach the same depth or surface level, the more nearly equal will be the pressure in both shafts, causing the current of air to circulate, and hence the greater likelihood of it stopping altogether at times. In mines where ventilation is effected by natural causes, it is no uncommon occurrence for the air * 120 ft. at 62" F. is only approximately correct, as the temperature would be different at different points in the shaft. 366 PRACTICAL COAL-MINING. in summer time to be travelliDg down one shaft in the morning, to come to a standstill in the middle of the day, and circulate in the opposite direction in the evening. In most mines, therefore, natural ventilation is totally inadequate, and should not be depended on where fire-damp or other dangerous gases are given off. Waterfall Ventilatioii. — To set a current of air in circulation in a mine by means of a falling column of water is not a method that is very commonly resorted to, nor is it to be recommended, except in cases of emergency, such as the sudden stoppage of a fan. The author has known cases where the plan proved, however, of much service in ridding the workings of a body of choke-damp, but in this case it was only adopted as an auxiliary to the circulation arising from natural ventilation, and had there not been plenty of surplus pumping power to raise the water to the surface again, it could not have been used at all. This method can only be used economically when there is an adit level connected to the shaft, and which will convey the water from the workings without the employment of machinery. Furnace Ventilation. — A number of years ago nearly all collieries of any importance were ventilated by means of furnaces, but this system of ventilation has fallen into disrepute, and now few collieries, except in some districts in the north of England, are supplied with air in this manner ; and the employment of furnaces for this purpose is within measurable distance of ceasing altogether, as it has little to recommend it. The action of the furnace is very simple. The current of air, in passing over the fire, is heated, which causes it to expand, and its density being lessened, it can no longer resist the pressure of the denser and heavier column of cold air behind. Hence it is continu- ously driven forward into the up-cast shaft, and a current thereby established, while the higher the temperature of the heated air, the greater will be the quantity that will pass over the furnace. The power of a furnace therefore depends on the amount of heat which it can communicate to the current of air; and as the efficiency of a furnace depends on what is known as the height of the motive column, it necessarily follows that the greater the depth of the up-cast shaft, the greater will be the quantity of air passing.* The motive column is a head of air of the down-cast temperature and of such a height that it will equal the (Hfference of the weight between the air in the down-cast and up-cast shafts ; or simply, it is the difference in height between two air columns of different tempera- tures due to their different densities. The motive column can there- fore be expressed in terms of its height in lineal feet and inches, in terms of ventilating pressure expressed in lbs. per square foot, and in * In furnace ventilation the quantity passing varies as the square root of depth of up-cast shaft VENTILATION. 367 terms of ventilating pressure represented by inches of water gauge, each of these terms being convertible. The following formulae will show how the motive column may be expressed in each of these terms: — Let M = height of motive column in feet P= pressure in lbs. per sq. ft. A = motive column in inches of water gauge. D= depth of up-cast in feet. d= >t down -cast in feet. ^= absolute temperature of air in down-cast shaft * ^= absolute temperature of air in up- cast shaft. 1^3= weight of 1 cub. ft. of air at 32 i^hr. and 80 ins. barometric pressure (147 lbs. per sq. in.). |)= weight of 1 sq. ft of water 1 in. deep (6 '2 lbs.). Then M = D ^"^» k = wU^^~^ P^ (1) (3) (6) orM = w or P — M X tr or A= (2) (4) («) Example, — If two shafts are each 100 fms. deep, and the temperature of the air in the furnace shaft is at 160** F., while in the other or down -cast shaft it is at 60** F. , what would be difference of pressure, and what height of water gauge would this represent? Taking formula 3 we have the difference of pressure : — P= -080728x600 (460 -H 60) -(460^00) 460-1-160 = 48-48 ^20_-620 620 = 48-48 100 620 = 7*8 Ibi. persq. ft and the height of water gauge A-^ = l-5ins. 6-2 These results are only approximately correct, as the weight of a cubic foot of air is taken at 32* Fahr. and 14'7 lbs. pressure per sq. ft. ; to get it mathematically correct the weight of a cubic foot of the air would have to be calculated for each shaft and the average taken, but the difference is so small that this may be neglected. Example, — If the temperature of the down-cast shaft is 50* Fahr., the depth of the up-cast shaft 800 yds. , what would the temperature require to be to give a water gauge of 2 ins. f * Zero on the absolute scale may be taken as - 492" Fahr. (460 -f- 32) below the melting-point of ice). 368 PRACTICAL COAL-MINING. By formula 5 we have h=wD ^—^ and transposing we have Substituting now the values we have ^ ^ ' 0-080728x900 h 510- -72.65- Transposing we have (t,- 510) X 72-66 = 4784 + 10-4<2 and 72-65^- 37051 -6 = 4784 + 10 -4/, 72-65<8- 10-4^=4784 + 37061 -5 62-25^ = 41835-6 . , _41835-6 • * ^""62-26~ or = 672* absolute 672-460 = 212** F. Taking the first example to find the motive column, we have M=600 }4^ ~~=96'9 ft. 160 + 459 and p=Mxtr=96'6x 0*08072 = 7 '82 lbs. per sq. ft., the same as before. The water gauge may also be expressed in terms of the motive column, h = -=— — . It will be observed that the motive column, 52 as ascertained by the above formula, is at the temperature of tlte doum-cast shafty and at a pressure of 14*7 lbs. per sq. in. Now it is evident that if ' motive column ' is to be used as an expression of ventilating power, the motive column of each mine must be reduced to some definite standard. This standard, as given by Mr Atkinson, is the temperature of 32* F. and 14*7 lbs. per sq. in. atmospheric pressure ; therefore, to ascertain the motive column under any conditions of temperature or pressure^ and reduced to above standard, the formula will become . /l'3253xB\ /l-3253xB\ j S=]V459 + ^, ) VJ59+1j/[d . . . (7) ( "080728 ) where S = standard motive column B = height of barometer in inches /26 6 or 1 Vioo 10 2 Hence an up-cast shaft 100 fms. deep would give twice the quantity of air that one 25 fms. would give, all else being constant. Take, again, the temperature ; suppose the mean temperature of the down-cast is GO"* F. and the up-cast 85" F., and assume that the latter temperature has been increased to 160" F., then the quantity of air passing will be in the ratio of V86j260 = V26 = 5 or 1 yieo - go >/ioo 10 2 Hence the quantity of air will be doubled. Again, the efficiency of a furnace varies directly as the fuel consumption, therefore the horse-power for a given fuel consumption varies inversely as the depth, and may be shown as follows : — Depth of shaft in ft per Fuel consumed horse-power per hour. 250 ft 96 lbs. 500 „ 48 ., 1000 „ 24 „ 1500 „ 16 ,. 2000 „ 12 ,. 3000 ,. 8 „ 4000 „ 6 .. 24 370 PRACTICAL COAL-BflNING. This table shows that, before a furnace can become as efficient as an engine working a fan, in regard to the fuel consumed, the shaft would require to be nearly 3000 ft. deep, as an engine for driving a fan, if in good condition, should not, on an average, consume more than 8 to 10 lbs. of coal per horse-power per hour. The difference in cost and upkeep between a fan and furnace plant, both dealing with the same quantity of air, may be taken as under : — (1) FanSf etc. Approximate Price. Two double- fined Lanca- shire boilers 80 fL x 7J ft, . . . . £760 0 0 Guibal fan 40 ft x 12 ft (32 to 85 revs, per minute), with engine complete, . . . 1100 0 0 Building8,forenginehouse, fan casing, eta , . . 500 0 0 Sundries, . . . 100 0 0 Total, £2460 0 0 (2) Cost of Fwnuue, Approximate Priee. Estimate for building and material, . . . £150 0 0 Making ' dumb • drift,' etc. 100 0 0 Total, £250 0 0 Co8t per annum (865 days). 0 0 0 0 Cost per annum (865 days). Interest on £250 at 5 per cent, .... £12 10 0 Depreciation at 5 per cent, 12 10 0 Repairs, . . . . 5 0 0 Triping, 8} tons per 24 hours at 8s. per ton, . 479 1 8 Attendants' wages, three men at 8s. 6d. each per day 191 12 6 Total, £700 13 9 Interest on £2450 at 6 per cent . . . £122 10 Depreciation at 5 per cent, 122 10 Repairs, . . . . 10 0 Stores, furnishings, etc.. . 10 0 Dross for boilers (8| tons — — ^— ^^ per 24 hours at Is. 6d. per ton), . . . 102 13 1} Cost of furnace per Enginemen's wages (two annum, . . £700 18 9 at 48. per shift), . . 146 0 0 Oost of fan per annum, . 518 18 1} Difference in favour of Total, £513 13 1^ fan, . 187 0 7} If the item for enginemen's wages (£146) be omitted — and as at most collieries the winding or other engiuemen attend the fan along with their other duties — then the difference in favour of the fan per year would be £333, so that the saving per annum would cover the entire cost of a fan installation in about seven years. The shafts for which the plant in the above estimates was required were 125 fms. deep. In a more shallow mine the fan would compare to even greater advantage. In the erection of furnaces the greatest care ought to be taken to minimise risk against fire ; the side walls should be 14 in. to 18 in. thick opposite the bars, with plenty of room for a current of air VENTILATION. 371 to circii.ate outside them, and if the furnace in built near to a Beam of coal, it should be provided with a double arch, and apace left between for a current of air to circulate through to keep the outeide cool ; the space between the outside arch and the strata being filled with sand and ashes, which are bad conductore of heat. Fig. 410 shows the construction of a ventilating furnace. In mines where the return air contains fire-damp in dangerous quantities it must not he allowed to pass over the furnace, as it would ignite and cause an explosion, but should be led into the up-cast shaft by a separate way, termed a 'dumb' drift, at some distance from the furnace drift, or it may enter the shaft on the opposite side from the furnace, higher up the shaft, or by another seam, or from the workings of a lower seam, if the furnace be placed Fio. *10.—7ontil«ting furnace. far enough back to prevent the flame of the fire from entering the shaft (figs. 411, 412). In such cases the furnace must be fed with pure air direct from the downcast, or from some section of the workings sufficiently pure for the purpose ; in either case the efficiency of the furnace would be greatly reduced. When such is the case, the fire-bars are fitted with doors, so as to foree as much air through them as possible, and in this way the air is raised to a higher temperature ; if only a certain quantity of air is required to assist combustion, the space below the fire-bars may be fitted with doors, and the air brought from the down-cast in pipes, the supply being regulated so as only to let as much past as is necessary to seciire complete combustion. If the fire bums feebly from the presence of black-damp (CO,), a similar arrangement is necessary. In cases where iron tubbing is used for lining the shaft, it ought to be protected by an inside lining of fire-brick from the destructive fumes and heated gases given off from the furnace. Aa fire-brick is a bad conductor of heat, less heat, and therefore tees energy, will be 372 PRACTICAL COAL-MINING. lost than if the air were in direct contact with the iron tubbing during its passage up the shaft. Speed of Air in Up-cast. — The speed at which the air travels in the up-cast varies very much according to size of the shaft and the extent of the underground workings, and may range from 20 to 50 ft. per ',....',// I.I!... ■/..// Figs. 411, 412. — Diagram of furnace ventilation. second, accoixling to the quantity of air passhig, and the area of the shaft. The use of furnaces underground for ventilation is objectionable and not to be recommended, especially in mines in which fire-damp is given off, the only thing that can be said in their favour being that they are very much cheaper as regards first cost than fans. They have, however, many disadvantages, among which may be noted : — VENTILATION. 373 The ponsibility of an explodon from a sudden outburst of cas. Shaft repairs can only be carried out with great inconvenience, if the up- cast is used as a winding pit. The expense incurred for fuel and attendance is heavy compared vdth that required for fans. Where iron tubbing, rope, or iron guides are used in shafts, great damage is done to them by the gases given off from the furnaces, and also by the expansion and contraction due to the variations of temperature. The circulation of air by means of furnaces may become very unequal, depending often on the management of the man in charge. Mechanical Ventilation. — Mechanical means of ventilation may be divided into two classes, viz. : — Statical ventilators = Displacement machines or air pumps. Dynamical ventilators = Exhausting or compressing fans. Statical ventilators are now so little used for mine ventilation that they need not be described here. Fans. — The principle on which all centrifugal fans act is known as centrifugal motion. In the case of a fan the centrifugal force drives the air from the centre, the particles being revolved in a circle by the fan until thej are finally thrown off at a tangent, thus creating a partial vacuum at the centre, which causes a further supply of air to enter, and thus establishes a continuous current. In general, such ventilators are used to exhaust the air, and are usually placed at the top of the up-cast shaft, but they may also be used as forcing or compressing machines, in which case they would require to be placed at the top of the down-cast. Of centrifugal ventilators there are now a large number in use, but those most in favour are the *Guibal,' * Waddle,* *Schiele,' and ' Cappell ' types, the others being all, more or less, modifications of one or other of these. Guibai Fan. — This fan is usually constructed of large diameter, 20 to 45 ft., the width being J to ^ of the diameter, while the central opening is about ^ of the diameter. The Guibai fan works in a brick casing, exhausting the air into an cvasiie chimney, and is now usually fitted with a movable shutter a, to regulate the opening for the flow of air. The fan itself is made of eight or ten straight blades, fitted on to a central casting (figs. 413, 414) ; in large fans the blades are made of wrought iron, while for small fans, 10 ft. or so in diameter, they may be of wood. The chief objection to this fan is its large size and con- sequent heavy cost, and also the large outlay for fan chamber and foundations. The great width, moreover, causes a very heavy weight to be distributed over a long length of driving shaft, which can only be supported at each end, and consequently requires very heavy shafting, while instances have occurred where the shafting has suddenly snapped, through the weight. The Guibai fan has, however, from recent experiments, proved to be a very efficient ventilating machine 374 PRACnCAl COAL-HININQ. under widely varying conditions. The speed of the fan varies with the size, a fan 30 ft. diameter being usually driven at from fifty to sixty revolutions per minute, and one of 40 to 45 ft. diameter at forty to fifty revolutions per minut«. Waddle Fan. — This type of fan is of the lai^e open running description, and is the best of this class of ventilator. It requires no fixed casing or chimney, but delivers the air all round it« circum- ference direct into the atmosphere, and therefore its width is reduced at the periphery, which causes it to be very narrow, in proportion to its diameter, compared with the Uuibal fan. Its diameter varies from 20 to 50 ft., the blades a b being 12 in. to 18 in. wide at the circumference, and 2^ to 4 ft. wide at the centre, and fixed into the Fioa. 413, 414,— GniUl tan. casing c c, both catsiug and blades revolving in one piece (figs. 416, 416), which tends to reduce the vibration, which is so noticeable a feature in the Uuibal fan. All the Waddle fans are now being made with a diverging outlet, i.e. the two rims projectnig beyond the blades are inclined outwards. This tends to reduce the velocity of the air as it leaves the circumference, and also requires less power to drive it. Its speed is forty to sinty revolutions per minute. Some of the advantages claimed for this fan are : — Being direct driren, it cauBes little noise and vibration. As it requires no encloBed casing or ehimney, the first e foandatioDa, etc., ia snull. TOO small eost for repairs per annum. A lugn percentage of the power employed is rendered etTpctive. The vibration and wear and te«r — '— " " " "- "-"-' '- of muonrf for t less tbai n the Ouibal fan. VENTILATION. 375 Schiele Fan. — This fan is somewhat like the Guibal in ita con- struction. It has the same expanding chimney, but instead of ths blades being straight, they are curved from the centre, and the casing is open, while the width of the blades is not the Bame throughout, \i Fios. 41G, 41fl.— Waddle fan. but greatest in the middle, decreasing towards the centre and the tips (figs. 417, 418). The air is taken in at hoth sides of the fan, which may be driven either direct or by belting, the httter method being the moat common. In size the fan varies from 5 to 15 ft. in diameter, with a width at the circumference of 1 to 3 ft, and at the 376 PRACTICAL COAL-MINING. centre of 2 to 4 ft. The speed varies from 120 to 400 or 500 revolu- tions per minute, according to size. Its chief advantages are : — (1) It is moderate in size, and occupies little space at the surface. (2) Freedom from vibration and small cost for upkeep. (8) The shaft bearinss, not beinff in the return airway, are easier seen and more readily available tor repairs. Cappell Fan. — Like the Schiele, this fan is of the small quick- running type. It is constructed of two concentric cylinders, an outer and inner one, each having six curved blades or vanes, the convex sides of which are in the direction of rotation (figs. 419, 420). Fio. 417.— Schiele fan. The cylinders (1) contain port-holes (2) between the two sets of blades, the air passing through these port-holes between the inner and outer chambers ; the air is taken in at the centre and thrown off the inner blades into the outer chamber by centrifugal force at a high velocity. It then strikes against the outer blades, and gives back the greater part of the impulse received from the inner blades, which reduces its velocity when discharged. Velocity imparted to the out- going air always, it should be noted, diminishes the efficiency of the fan.* In size this fan varies from 8 to 15 ft. in diameter, with a width of 7 to 11 J ft., and it is worked at speeds of 180 to 300 revolutions per minute. The advantages claimed for this fan by the makers are : — (1) It can do a large amount of useful work in proportion to its size. (2) Smallnees of fan reduces the capital outlay. (8) It can withdraw large quantities of air. The latest type of this fan is shown m figs. 421, 422. • Or^. and Stone Mining, Sir C. Le Nrve Foster, sixth edition, p. 532. VENTILATION. 377 Walker Fan. — This fan (fig. 423) is constructed somewhat like the Guibal, but it also combines other types. It may be termed a medium-sized fan, as it is generally from 20 to 25 ft. in diameter. It is built exclusively of iron and steel. On the main shaft are fitted two strong cast-iron bosses, which extend lengthwise on each side towards the journals, thus distributing the weight of the fan over a considerable portion of the shaft. Between the bosses are placed two t — .-EIIVJ I I Fig. 418.— Schiele fan. discs of steel, of uniform thickness, bored in the centre to fit the fan shaft. Between these two discs, and gripped tightly by them, are fixed the iron arms of the fan in pairs. These arms extend from near the axis of the fan to its periphery, being supported half-way by the discs. In the small spaces between the discs which are not occupied by the fan arms, there arc inserted annular plates. The whole portion outside the boss is then securely riveted together. Angle irons are riveted to the fan arms where they extend beyond 378 PKACTICAL COAL-HININQ. the discs, and to these, eight in number, are firmlj secured the cross- section of the arm tuid vane in the form of a, letter T, the top of the T representing the vane and the surface pressing against the air. The vanes, which spring tangentially from a small circle concentric with the fan shaft, are curved longitudinally to the arc of a circle of Figs. 41S, 420.— Cappell f&n. a certain radius, and are cut away from the edge of the inlet to the fan sbaft to minimise centtui resistance. It is very necessary to minimise the slipping of the air between the sides of the vanes and the walls of the fan chamber. The vanes cannot be brought too close to the walls, as, in the event of any side movement, they might Fiaa. 421, 422.— Uteat ^pa of C>pp«U bn. catch and be injured. This clearance space is, therefore, filled up by attaching strips of pliable hoop iron to the sides of the vanes. The fan is also fitted with the Walker anti-vibrating shaped shutter. In the ordinary Guibal fan, as each blade or vane passes the tower edge of the shutter, a pulsatory action of vibration takes place. This vibration is caused by the too abrupt cessation of the delivery of the air from the fan vanes or blades as they pass the opening to the chimney, and for this the shape of the regulating VKNTILATION. 379 shutter is responsible. The upper part of this opening, fonned b; the shutter as hitherto constructed, has a line parallel b> the tips of fan vanea, and aa the fan revolves these lines become identical ; the delivery of the air is, as a consequence, abruptly interrupted. While discharging the air, the pressure is against the front of the vane, but immediately the latter enters the fan casing the load upon it is suddenly removed, and the pressure, owing to the vacuum within the casing, is instantaneously reversed, and causes an upward rebound of the previously depressed blade, with the result that a dangerous degree of vibration is set up. The Walker auti-vibrnting shutter, aa attached to the fan, removes this evil by effecting a perfectly gradual change in the pressure on the vanes, and so governs the discharge of the air as to cause it to pass, without objectionable eddying, in a continuous atream from the fan vanes into the chimney, instead of intermittently, and without the pulsatoiy action described. Fro. 123.— Walker fsD. The shutter is constructed in sections, any of which can be removed for the purpose of adapting the area of the opening to varying duties of the fan. The fan is usually driven by rope gearing. Sdfction of a Fan.— It is desirable, when erecting a fan to do a given amount of work, to select it so aa to suit the varying conditions under which it must act. The height and condition of the under- gromid roads are very important factors in determining the type of fan to be selected, also the amount of room at disposal for surface ansngements ; but the principal considerations are: (I) the useful work or effect given out by any fan or enguie ; (2) the first cost of fan and engine, and of foimdations, engine house, fan drift, etc. ; (3) the space required at the surface for fan and engine houses, etc. ; (4) the relative economy of fuel and stores consumed by the different types of fans ; (5) the cost for repairs and freedom from stoppages and breakdowns. In coming to any decision, especially on the basis of a maker's 380 PRACTICAL COAL-MINING. estimate, it is nearly always safe to make a deduction of 25 to 30 per cent., taking the amended estimate of the useful work that will be performed, for afterwards, in practical working, it may be found that the maker of the fan has overestimated the merits of his machine by that amount, and it is always better in any case to have a good deal of surplus power in case of an emergency. Medium-sized and small fans wuth quick-running engines are now being largely used, and have a good deal to recommend them, as they are economical and safe in working and take up little space. One objectionable feature, however, is the noise which they make while working, which is very disagreeable, especially at collieries situated near to towns. It should also be remembered that small fans cannot produce volumes of air equal to those produced by large-sized fans, as the orifice of discharge, which determines the resistance of the fan to the passage of the air, must necessarily be less for a small than for a large fan. Where large volumes of air are required with a low water- gauge, a fan of large volume will, therefore, be most suitable. It is desirable in most cases, and in fiery mines almost indispens- able, to have a duplicate set of engines, either of which can be im- mediately attached to the fan in case of a breakdown. Sometimes a duplicate fan is set up, both fans being comiected to the fan-drift, so that either can be worked separately for a week or a fortnight at a time. Examples of these arrangements can be seen at Eamock Colliery, Hamilton, and Auchinraith Colliery, Blantyre ; at the former there is a duplicate set of engines, while at the latter there is a duplicate fan. Dimensions of Fan for a Given Quantity of Air. — ^This is not a matter that is very easily determined, and in erecting a fan it is always as well to get practical details of the work performed by other fans at work in the same neighbourhood, i,e, imder much the same conditions. Mr A. L. Stevenson says the actual size is to some extent a matter of practical experience, and he recommends the following dimensions for varying volumes of air : — Under 50,000 cub. ft per minute, 30 ft. diameter. 50 to 100,000 „ „ 35 „ 100 to 150,000 ,, „ 40 „ Compressing Fans. — According to the Coal Mines Regulation Act, fans require to be placed some distance back from the mouth of the shaft, and the top of the shaft ought to be lightly covered over to give way easily in the event of an explosion occurring. Fans, as already noted, may be either compressing or exhausting. The former require less power to drive them than the latter. The exhaust fan rarefies the air in the interior of the mine and accelerates the escape of gas from the waste workings. The compressing fan, on the other hand, renders the air in the mine denser and lessens the escape of gas. A falling barometer would intensify the evil of using an VENTILATION. 381 exhaust fan by rarefying the air to a still greater extent. At the same time, it is safer to employ a fan which promotes the escape of gas from the workings, provided there is an ample supply of air available with which to dilute it. In the case of a colliery where choke-damp is given off in the workings, it might be advisable to use a compressing fan to prevent the escape of this gas into the working faces. At the Clyde Collieries, Hamilton, experiments were made with com- pressing and exhausting fans, the results of which gave an apparent advantage to the compressing type, but the experiments were not carried out fully enough to allow of definite conclusions being arrived at. There are cases, however, where compressing fans have been used to advantage, and give a larger quantity of air than an exhaust fan imder the same conditions. One such case, with which the writer is acquainted, was at a small colliery where there were two shafts, one about 90 fms. deep and the other 50 fms. ; and as they were separ- ated by a distance of 800 or 900 yards, and no coal was being drawn from the deepest shaft, it was desired to remove the fan which was on this pit to the other one, to save boiler power. This was done ; and when it was fitted up, at the 50 fms. pit, as an exhaust fan, it was found to be totally inadequate to supply the quantity of air required. It was then altered to a compressing fan, making the deep pit the up-cast, with the result that nearly 50 per cent, more air was circulated in the workings. In this case it was a distinct advantage to have the fan forcing instead of exhausting the air ; but the superiority of the compressing fan in this instance may have been largely due to the assistance it received from natural ventilation, owing to the deeper shaft having been made the up-cast, and the apparent inferiority of the exhausting fan may have been due to the fact that it had to draw the air from the deep shaft through a long stretch of old workings. If a forcing fan is used, the dow^n cast shaft must be covered over, which renders it inconvenient for winding, pumping, and haulage ropes, etc. Again, in the event of an explosion occurring, the disastrous effects and force of the explosion are nearly always felt most keenly in the down-cast shaft; and if the ventilation was carried out on the compressive principle, the fan would in all probability be wrecked by the force of the explosion, putting a stop to the circulation of air when it was most required. On the other hand, with an exhausting fan placed on the up-cast shaft, an ex- plosion might occur and the fan remain intact, which is a great advantage under such circumstances. Taking everything into account, and the fact that the great majority of collieries are ventilated on the exhaustive principle, it would appear that the exhausting fan is the most suitable for general colliery work. Equivalent Orijice. — The theory of the equivalent orilice of a mine was first investigated by tlie French engineer M. Margue, and may be stated thus : — The air |>as8ing tlirough the workings of a mine meets with a certain amount of resist- 382 PRACTICAL COAL-MINING. ance. If we imagine that all the air is entering, not through the mine woridnca, but through an orifice or aperture in a thin plate, then the equivalent orifice for any mine would be the a])ertuTe in that plate, of an area such that a resistance would be offered to the entrance of the air equal in amount to thai caused by the mine workings. If we call Q the quantity of air in thousands of cub. ft. per minute, h the water-gauge in inches, and A the area of equivalent orifice in sq. ft, then A=— yr (a) Q Av^t . . (6) ^ 0-37 ^ ^ VA=^^. orA-0-1869C^-y . . . . (c) or, assuming the normal densities of the air and water to be in the ratio of 1*2 : 1000, and Q as before, = the volume of air in thousands of cubic feet per minute ; A = inches of water-gauge, then A=0-403-%. fjh Quantity of Air delivered by a Fan. — The quantity of air delivered by a fan is not easy to ascertain, as no two fans, even of the same make, will give the same quantity, even when tried under the same conditions. A great deal depends on tne condition of air-courses, type of fan, etc. The height of the motive column H in feet of air, produced by a diiference of temperature or by mechanical means, is the cause of air currente circulating in mines, and the velocity of such air currents (provided there is no resistance or friction) would be equal to that acquired by a oody falling from the same height as that represented by the motive column v^\/2gK, and therefore the theoretical volume of air passing through any opening (equivalent oriHce) of area a will be V=ra, buta8t>=V2yH .'. y=a^2gH. ; butH = — .'. V = ax/2i7— = «n/2u* 9 ^9 The theoretical volume produced per second, allowing for the action of the vena contracta, will be V = 0-65aV2M3. Applying this to a fan with a tangential velocity in feet per second = u, and a manometrical efficiency = E, then V = -65axV2«^xK. or if Q = total quantity of air in cubic feet per minute, d= diameter of fan in feet, R= revolutions of fan per minute, ti= tangential speed of fan in feet per minute =«I x 3*1416 x R, a = equivalent orifice of mine in square feet, K= coefficient representing the manometrical efficiency, 0*65= coefficient of the vena conirada^ then Q = 0*66a\/2(rf>rir"x R)2 x K =0*65 x 1-41», a, rf, R, K = 2-88 o, d, R, K or d = Q 2-88 a, K, K Example, — What would be the total quantity of air, in cubic feet per minute, produced by a Guibal fan 35 ft diameter and moving at a speed of 40 revolutions per minute ; the equivalent orifice of the mine being 30 square feet, K being = *69 Q = 2-88x30x35x40x -69 = 83,462*40 cubic feet per minute. VENTILATION. 383 Example, —What size of fan, making sixty revolutions per niinntc, and giving an efficiency of 60 per cent., would be required to pass 60,000 cub. ft of air |)er minute, the equivalent orifice of the mine being 20 sq. fL T This problem may be worked out in two different methods, but we may proceed 0-87Q by the formula, a= ^ • V'* To find the water-gauge — 0-87 X ??52? ^^"- .-. 20VA=22.20 and A = (2^^)*=l-28 ins. We may find the velocity of the periphery of the fan by formula h= '00045 %fl. Then 1 -28 = -OOOISii^ or «•= ^-^ and w=62-82 ft. per second. As the fan is making sixty revolutions per minute, the diameter, supposing its efficiency to be 100 per cent, would be v X 60 52-82 X 60 20= - ^i?? Rx3-1416~60x 8-1416 X 69 = 24-22 ft. But the fan has an efficiency of 60 per cent only, and allowing '69 for mano- metrical efficiency, .-. the diameter =^?^1^ = 40 ft., 60 X '69 80 that to pass a volume of 60,000 cub. ft per minute, with an equivalent orifice of 20 sq. ft., we would require a fan 40 ft. diameter, making sixty revolutions per minute. Working it out by the more direct formula given above, we have d= ?222? =25 ft 2*88 X 20 X 60 X '69 and allowing for 40 per cent in loss of efficiency d=25xl00^4^.gf^ 60 It should be remembered that these formulae only give approximate results and are not mathematically correct. A more exact approxi- mation of the actual volume of air produced by a fan would be found by the formula where a =» equivalent orifice in sq. ft. and 0 = orifice of discharge of the fan in sq. ft. or an orifice representing the difficulty of the passage of the air through the ventilator. The value of 0 is a variable quantity, depending on the equivalent orifice and the water-gauge, and may be found from the expression h a^ ha^ ^'^hlhrOOOOVou^K^h'^ ^^"^^^ ^''"« respectively the theo- ^ h^a^ ha^ retical and observed water-gauges.* * Students who desire a fuller treatment of fan ventilation should consult Theories and Practice oj Centrifugal Machines ^ by D. Murgue (£. & F. N. Spon, 1888). 884 PRACTICAL COAL-MINING. The water-gauge (theoretical) that can be obtained from a perfect fan may be found from the formula A= - , where /i= ventilating pressure in height of air column, and v^= velocity of periphery of fan in feet per second. Take the speed of fan periphery at 90 ft. per second, K=-— — 253*12 feet, and with a column of 253*12 ft. of air, say at 70* F. and 30 in bar., the pressure ^V8253j<^^ 253*12 = 19*02 lbs. per sq. ft., and the W.G. =!?-?? or 8*65 ins. 70x459 r --1 » g.2 d X WG The same result may be arrived at by the formula h= . i ^ ^ d,xl2 where h is the height of motive column as before ; W.G. the height of water-gauge in inches; d the density of water = 1000; and d^ the density of air 1 -2. The effective water-eauge= theoretical W.G. xK (or manometric efficiency) and the value of K for different fans varies for different sizes. The manometrical efficiency is the ratio of the water-gauge observed in practice to the theoretical water-gauge deduced from calculation as shown above, or by the formula h = ^^ ; to being the weight of 1 cub. ft. of air at temperature of shaft •I* Relatively, the value of K for Guibal fans is '69, that for Waddle fans '60, and for Schiele fans '50. In fans of the Guibal type the acttuil water-eauge is often more than the theoretical W.G. (from ^ to i), but this is not always the case, as it is some- times less. The amount of usrfiU effect produced by a fan is found by carefully measuring the quantity of air put in circulation and measuring the water-gauge ; the U. P. • 4.U QxW.G. x5*2 m the air =-2 — ^^^^^ 33000 While the air measurements are being taken, the speed of the fan engine is carefully noted and indicator diagrams taken, from which the mean effect of steam pressure acting in the cylinder is ascertained. Then the H.P. of engine = ^^ "" ^^^^3^00 ^ ^ ^ "^ ^ , where D is the diameter of cylinder of engine in inches ; P, the effective pressure of steam acting on piston in lbs. per sq. in. ; L, the length of stroke in feet ; and R, the revolutions of crank per minute. Then the useful effect of fan will be as H.P. in air : H.P. in engine. Example. — If the total quantity of air passing is 160,000 cub. ft. per minute with a W.G. of 2 in., the fan engine bein^ 20 in. diameter with a 3^ ft. stroke, going at forty revolutions per minute, with an effective steam pressure of 40 lbs. per sq. in., what would be the efficiency of the fan ? „ „ . 160000x2x5*2 ^A.io H.P. in air= — — — =50*42 83000 „ r, • 18-x *7854x 40x3*5x2x40 ^^.^^ H.P. m engine = - - «-^^^- — =86*36. ^ 33000 The efficiency of the fan will therefore be as 50*42 : 86 36 or *58, which multiplied by 100 = 58 ycv cent. VENTILATION. 385 The quantity of air produced by a centrifugal ventilator, if the speed remains constant, varies (1) inversely with the resistance of the mine, and becomes zero when the resistance of the mine is infinite or when the inlet from the mine is completely closed ; and (2) varies as the orifice of the fan (0) or the orifice of the mine (a) is increased or decreased. The quantity of air produced also varies with the speed of the fan, other conditions remaining constant. The above formula also demonstrates that the quantity of air produced by small fans can never equal that produced by large fans, as the orifice of the ventilator, which measures the resistance of the fan to the passage of the air, must necessarily be less for a small than for a large venti- lator, hence better and more efficient results can be got by employing medium-sized fans, 20 to 30 ft. diameter, especially where the seams worked are a fair height and where the airways are of fairly good dimensions and can be kept in good order. Speed of Fan. — This will altogether depend on the size and weight of the fan, for there is a limit to the angular velocity at which a fan may be driven, and to go beyond which would be dangerous. As a rule the velocity of the periphery may vary from 90 to 110 ft. per second, the latter being a practical limit for medium or large-sized fans. Advantage of Fans over Furnaces, — (1) They will not ignite gas ; (2) are more under command and better suited for repairs ; (3) the quantity of air passed is more regular and more easily varied at will ; (4) less cost incurred for upkeep and attendance, and smaller con- sumption of fuel, stores, etc. Cost of Fans. — The price of fans is a very variable item, but the following are taken from some makers' estimates for fans to deliver 120,000 cub. ft. of air per minute, with a water-gauge of 3 in.* SckieU Fan, 10 ft. diameter, with engine 20 in. diameter x 24 in. stroke, with driving belt, etc. ...... £600 Waddle Fan, 21 ft diameter, with engine 20 in. diameter x 21 in. stroke, complete, ....... 590 Onibal Fan, 27 ft. diameter, with engine 18 in. diameter x 36 in. stroke, complete, ....... 350 Chandler Fan, 13 ft. diameter, with patent silent running Chandler engine, ........ Walker'8 Patent Fan, with patent anti- vibration shutter, engine 16 in. diameter X 14 in. stroke, ... 503 Cappell Fan, 12 ft. x 5 ft. 6 in. open running, with semi-compound engine 16 in. diameter X 36 in. stroke, .... 360 In addition to the above prices, the brickwork for a Guibal fan would cost on an average £130 to £150, and that for a Cappell fan about £70. 700 ♦ These prices were quoted in 1896 ; in 1900 they were 20 to 26 per cent, higher. At the present date (1905) they may be taken about the same price as for 1900. 25 386 PRACTICAL COAL-MININQ. Auxiliary Underground Fans. — In underground work it frequently happens that long close or narrow drifts require to be driven in the solid coal or in stone-work, such drifts being only in communication with the main ventilating current at one end. When this occurs the drifts are difficult to ventilate — especially if they are long and fire-damp is given off — even with the aid of an efficient mid brattice. Under such circumstances a small auxiliary fan may be employed to assist the ventilation. If the quantity of air required for such work is not large, then a small fan rotated by manual labour may be employed, but if the drift is of considerable length and requires a larger quantity of air to keep it sufficiently ventilated, a fan of larger dimensions, say 2 to 3 ft. diameter, will require to be used, driven either by a compressed air or electric motor. The latter is the preferable method, owing to the ease with which a small motor can be installed at any position desired, and the higher efficiency which can be got from it, compared with a compressed air motor. The fan may be connected to the drift by either a dividing wood or brick brattice, wooden boxing, or large sheet-iron circular tubes, 1^ to 2 ft. diameter. Method of Driving Fans, — Fans working on the surface may be driven either — (a), direct ; (b) by belting ; (c) by ropes. Large fans of the Guibal or Waddle type, which are run at moderate speeds, are usually driven direct ; i.e. the coimecting rod of the engine is connected direct to the fan shaft through a crank or disc, and this, on the whole, gives good results and saves the extra cost of driving pulleys and belts or ropes. Small quick-running fans, of the Cappell or Schiele type, are usually driven by belts or rope gearing, the latter giving the best results, for although ropes are more expensive in first cost, they wear much better and are not so apt to give way as belting. The ropes may be eitlier made of hemp or cotton, the latter being now largely employed. Guiding and Conducting the Air Current. — In no part of colliery work does so much thought and care require to be expended as in the arrangements for guiding and conducting the difl!erent under- ground air currents. In many collieries large quantities of air can be measured in the intake and return airways near the shafts, but the actual amount that really reaches the working faces — the most important point — is often comparatively small. To ensure the maximum quantity reaching the working faces, the main air current will have to be split into as many currents as are necessary for each individual colliery, and each of those currents carefully conducted to the working faces by means of air-crossings, trap-doors, bratticing, screens, etc. Air-Crossings. — When two currents, an intake and return, have to cross each other, an air-crossing will require to be constructed, so that they may not intermix. Where the strata are hard and free from open fissures the air-crossings may easily be constructclosiDg door. stone drifts are being driiren. When a close or stone drift has to be driven to any considcniblc length, and where the road has to be divided to Form uu iiitftkc and return airway, the central division is tiest made of masonry (tig. 431). If the roof is good, and no great cruriU anticipated, a IJ-in. brick wall may suffice, but it is best to build it 9j to 14 in. thick. Sometimes only a small brick quadmnt is built in roads where traffic is difficult, such as steep inclines or low-roofed ways (fig. 433). A half wall may be built, and a longitudinal plank laid on it, from which boards arc laid across to the side of the lieading (fig. 433), the seams in the top boards being well filled witli good clay, or mortar, and afterwards covered over with brattice cloth. Wood brattice, or a coniliination of wood with cloth, is largely used for short distances, such as occur in pillar and stall workings. To fix tlie brattice cloth, planks 1 1 in. x j in. arc nailed along the VENTILATION. 391 top of the props and at the bottom close to the floor. The cloth is fixed tightly to these planks, and also to the props, by means of short, flat-headed nails. The greatest care must be exercised in fitting the joints of the cloth, and in having such joints opposite a post, as well as in the fixing, top and bottom, for unless this sort of brattice is well fitted together, it becomes difficult to convey a current of air for more than 30 or 40 yards. In places where much fire-damp is given off, it is often difficult to keep the face clear by means of brattice at a distance of 20 yaids. In dividing the road by bratticing, the spaces for intake and return are generally of unequal area ; and in such cases it is the general rule to make the narrow way the intake, and the wide tram road the Figs. 431, 432, 433. —Ventilating close drifts. return. If the current of air is sluggish, this is undoubtedly the best method, as by making the small area the intake it will increase the velocity, and a supply of air may suffice to keep the face clear, which if brought in by the wider way would have been quite inadequate for such a purpose. If, however, the air can be supplied in large quantities, it can best be brought through the wider way. In longwall workings, fire-damp often accumulates at the face of the ripping, and in such a case a ' hurdle ' screen ought to be set up to clear it out (figs. 434, 435). A hurdle screen is fitted up by fixing a crown or strap across the road, and leaving a space 18 in. or 2 ft. between it and the roof. Two legs or props are set up to the cross- piece, and the screen-cloth firmly nailed to it. In all branch rods of a longwall working, screens must be fixed 392 PRACTICAL COALMINING to prevent the air, which ie generally required to travel round the faces, from passing sway, unless under exceptional circumstances. Fire-damp often aecumulatcB in the open spaceit between the packs in longwall, and is often very troublesome. When this occurs, it is cleared out either by conducting a current into such Hpoces by fixing a screen along the face, or by resorting to ' split buildings.' In this latter method the building or pack wall is not built right along, but at certain intervals a space of 2 to 4 ft. is left, and an airway formed through the waste, so as to clear out any accumulations of gas which may have lodged. Such airways are oft«n difficult to maintain and keep in repair, and new ones will require to be opened at short intervals. Air Pipes. — Instead of using brattice, wooden boxes or sheet-iron pipes are sometimes used, and are very convenient, but great care must be taken that they are efficient. Where such means are used the volume of air conveyed to the face may be sufficient to clear away the gas at the point of delivery, but at a short distance back from the face, where the velocity of air ia much reduced, gas may accumulate in dangerous quantities. The wooden air-boxes are made from 1 ft. to 2 ft. square, or even larger, and arc made of } in. boards fitting closely. Sheet-iron pipes from 1 ft. to 2 ft. diameter are also used. Laws affecting the Air Current. — A current of air, cither on the surface or underground, is produced, as has been explained, by differences of pressure or density. A very small dilTereuce of pressure or force is required to impart motion to the air, but a current travel- VENTILATION. 393 ling in a circumscribed area meets with a very large amount of resist- ance, which is termed friction, and of the total force or pressure required to set a ventilating current in motion a very large percentage is taken up in overcoming this friction. Roughly speaking, 90 to 95 per cent, of the actual force is expended in overcoming the resistance met with in the workings, while only 5 to 10 per cent, of the pressure is effective. If an air current in passing through the underground workings met with no resistance or friction, it w^ould flow with a velocity equal to that attained by a body falling from a given height, and could be ex- pressed by the formula v = j2glL, or approximately = 8 ^H, where V = velocity attained in feet per second ; H = height in feet fallen through ; and ^= value of gravity = 32*2. Before air will flow from one point to another, there must be a difference of pressure between the two points, and this difference in pressure can be measured as a head of air or motive column H, which may be substituted for the height, in above formula, through which the falling body has traversed. We have already shown that a head of air or motive column can be expressed in inches of water-gauge h= K^.n * ^ being = weight of 1 cub. ft. of air at the prevailing temperature and pressure. But the value of w=^—^^' and H = — : therefore the pressure in 460 + ^ 2(/' ^ inches of water-gauge required to set an air current in motion (with /I -3253 X B\ t^ •f X iiv ; V 46Q+"^7^2.7 no resistance) will be h= ^ts- • The laws of air friction are usually expressed as follows : — The pressure required to overcome the resistance due to the friction of air, when the velocity is constant, varies in proportion to the sur- faces in contact. The pressure per unit area required to overcome the resistance due to friction varies inversely, as the sectional area of the airway, or Poo — . a The pressure required to overcome the friction varies in proportion as the square of the velocity. Assuming that this latter law is correct (it is approximately correct for all except very high velocities), the force required to overcome friction is expressed by the formula, F = ksv^. Where F= force of friction measured in lbs. K= coefficient found by experiment S = total nibbing surface of the airway in sq. ft = total length x the mean perimeter in feet vs velocity of flow of air in feet per second. 394 PRACTICAL COAL-MINING. But v — -^,Q being = total quantity of air circulating in cub. ft. per second, and a = area of cross section of airway in sq. ft. If we assume that the resistance is overcome by a head of air, or motive column H, then we can also assume that it is overcome by an urging force F = Haw, which is the equivalent of this head. .*. Haw = Kfi(-^j (w behig = weight of 1 cub. ft. of air at given k sO^ temp, and bar.), from which we have H = — x ~, or in inches of to or water-gauge A = -^ x =7:-^. • w^ 5*2(a^) k The factor — is determined by direct experiment in mines. These are the three principal laws enunciated by the late J. J. Atkinson, and two other laws may be stated, which as a natural con- sequence follow from them, viz. : — The power required to overcome the resistance to an air current in ' the workings of a given mine varies as the cube of the velocity, and the resistance measured in lbs. per cub. ft. of air current is equal to the product of the coefficient of friction, the total contact surface and the velocity squared and divided by the sectional area of road, i.e. ^ KSV2 a The rubbing surface spoken of is the whole extent of surface ex- posed to the ventilating current, t.e. the roof, pavement, and two sides of the road, the sum of these four sides in section being called the perimeter. The total rubbing surface will therefore be the total length of airway multiplied by the perimeter. Exnmi)le. — lxi the aii-way 8 ft. wide, 6 ft. high, ond 200 fathoms long, what would be the total surface in contact ? Frictional or rubbing surface = (8 x 2) + (rt x 2) x 1200 = 33,600 aq. ft. Since the pressure increases in direct proiwrtion to the length, it follows that if we double the length of an airway the pressure will also require to be doubled, to maintain the same quantity of air in motion ; or, if the length be reduced one-half, the pressure required will be halved. Another point to be noticed is, that the pressure required to overcome the re- sistance due to friction depends largely on the size and shape of the airways, i,e» whether rectangular, square, or circular. In airways of each of these shapes, and having the same area, viz., 78*54 sq. ft., the perimeter of a circle would b« 81*416 ft., of a rectangle, 26*12 x 8, 58*36 ft., and of a square, 85*2 ft. VENTILATION. 395 From this it is evident that a circular-shaped airway presents the least area of rubbing surface of the three shapes enumerated, and hence would oppose the least resistance to a current of air passing through it ; but, on the other hand, it is the least practicable of the three, and one that is very seldom adopted, except in the case of vertical shafts. Since the pressure required to overcome the friction varies inversely as the area, it follows that in two airways, the areas of which are as 1 : 2, the pressure necessary to overcome the friction of an air current in them will be as 2 : 1, t.e. it would take a pressure of 1 lb. in the airway whose area is 1 to do the same work as a pressure of ^ lb. in the airway whose area was 2. In the case of two airways of equal lengths and perimeters, and consequently of equal rubbing surfaces, the velocity being the same in each case, but having unequal sectional areas, all the conditions upon which friction depends will be equal, therefore the amount of work required to overcome friction will be equal in both cases. We have assumed that the velocities are equal, therefore the totai. pressure must be the same in both airways ; but as the airways have different areas, the pressure per sq. ft. must be different, and will be less in the large than in the small airway. Example. — In two airways of e«|ual lengths, one 10 ft. x 8 ft and the other 14 ft X 4 ft., the ai'eas are as 80 : 56, while the nihbing surfaces are equal, and there- fore the total resistance or pressure must be the same in each. Suppose we have a velocity of 350 ft. jier minute in each airway, and that the total energy expended in overcoming resistance equals 120,000 ft., the total pressure for each airway will equal - ' — , i.c. 342 '85 lbs. ; the pressure i)er sq. ft. will, however, be different, for in the 10 ft. x 8 ft airway it will equal — ^-— , or 4 '28 lbs. per sq. ft, 80 342*85 and in the 14 ft. x 4 ft. airway or 6*12 lbs. )>er sq. ft, which is in the ratio 56 of 1 to 1 *42. From this it will be seen that the smaller airway requires nearly half as much more firessure per sq. ft. than the larger, and that the pressure varies in inverse proportion to the sectional area of the airways through which the currents have to pass. The pressure required to overcome friction is proportional to the square of the velocity. From this it follows that if the velocity be doubled, the pressure required to overcome the resistance due to friction will have to be increased four times; and if we halve the velocity, the pressure required will only be \. If we treble the quantity, the velocity must also be trebled, which will increase the original friction nine times. From the above laws are deduced nearly all the formula used in connection with problems in the ventilation of mines, and of which some may be here given. U pU the pressure {jer sq. ft., a the area of airway in sq. ft., s the total rubbing 396 PRACTICAL COAL-MINING. Barface of airway, v the velocity of air current in thousands of cub. ft per minute, and E the coefficient of friction,* iheu {I) pa=ksv\ (2) ;> = — , (I • ,„ „_ksv' ,,, ,._pa (.,, a---, (4) k-L^ i^) -e. (*)^^=D-'' = \/i^ whileiheH.P. = ^t*'^^ (7). 33000 Practical considerationB in reducing Friction. — Reducing the Length. — This can be most conveniently done when the airways are being constructed at first, and if the distance which the air current has to travel can in any way be reduced, even after the airways have been made, this ought to be done. There are many advantages to be gained by having airways as short as possible, amongst which may be mentioned : The smaller cost and reduced expense for repairs and upkeep, and the larger volume of air which can be obtained by a given expenditure of power. All sharp angles should be avoided as much as possible. Increasing the Area, — As to increasing the sectional area, there is a practical limit to which this can be done, depending largely on the nature of the strata through which the airways pass ; for sometimes it is only with the greatest difficulty that a road can be enlarged, especially if the roof or floor is very bad, and if there is a continuous crush on the workings. For this reason it is often cheaper and easier to make an additional airway parallel to the one already existing. By doing this the rubbing surface is doubled, and the resistance due to friction correspondingly increased ; therefore the pressure will also require to be doubled. At the same time, however, doubling the rubbing surfaces has also doubled the area, and consequently the velocity will be halved^ and the resistance and pressure reduced to one-fourth, the decrease of friction, owing to the reduced velocity in the larger area, being always much greater than the increase due to the extra rubbing surface. Example, — If an airway measuring 9 ft. x 6 ft. is enlarged to 9 ft. X 8 ft., the area will be increased from 54 sq. ft. to 72 sq. ft., or in the ratio of 3 : 4, and the velocity will be reduced inversely in the same ratio, i.e. from 4 : 3, while the rubbing surface will, at the same time, bo increased from 30 sq. ft. to 34 sq. ft., or in the ratio of 15 : 17. The resistance, however, varies as the square of the velocity, or as * For every foot of rubbing surface, and for a velocity in the air of 1000 ft. per minute, the friction is equal to 0*26881 ft of air column of the same density as the flowing air, which is equal to a pressure, with air at 32* F., of 0 0217 lb. per sq. ft. of area of section. This is known as the coefficient of friction. VENTILATION. 397 1 6 : 9, therefore the resistance, after increasing the Rrea, will be reduced to -^ of fj ( = JJ^), the net gain being over one-third. Another important factor in limiting the area of airways is the size of the ahftfts, for with small shafts of insufficient size to permit of the passage of the requisite quantity of air, it is useless to increase the area of air-courses beyond a certain limit. In making airways so as to present the least possible reaiBtance the following points should be attended to. They should be as nearly as possible of the same sectional area throughout, have as few sharp angles as possible, and no side projections and narrow places in them. They should also have a good-sized area, and be as nearly circular, or, if this is impracticable, as square, as possible. In experiments made recently by D. Murgue on the quantities of air passing in airways of varying construction, he found that there was a great deal of difference in the respective behaviour of arched air^ ways, timbered and untimbered airways (fig. 436). In workings of the same area he found that the quantities passed would be 46,000 cub. ft. per minute for arched airways ; 36,000 for airways with- out timber; and 32,000 for timbered courses, or in the pro- portion of ly'j:lj:l. Iteodings of the water-gauge for the sauie airways with these quantities ''"'"^'''^.^ti'mL^"."™*^''""^ ' were:— Arched airways, 0'253 in., '^ '^ jsa""'*^ airways without timber, 0-760 in., and airways with timber, 1-275 in., or in the ratio of 1:3:5 (approximately). These results show in a very etrilting manner the advantage of having good smooth passages for the air to travel in, and that often better results could be obtained by giving more attention to the air- ways than by trying experiments with l>ctter ventilating machines. For the different airways Murgue gives the following coefficients of friction, expressed as pressure per sq. ft. in decimals of a lb. for each square foot of rubbing surface and an air velocity of 1000 ft. per minute : — Arched pMsages, aTsnge coefficients '001713 Unlined „ „ „ ■00«4 Timbered „ „ „ -00821 The laws of ventilating may be summed up and briefly stated as follows ; — * The illmtratioa is intended to ghaw graphically tlist the arched airway will paw M much air with the same veatilating pmsure as either the ODliiied or timbered airwaya deaoribed on its ontaide. 398 PRACTICAL COAL-MINING. The quantity of air circulating in a mine is as the square root of the pressure or the square root of the water-gauge reading. In airways of the same sectional area, and which vary in length only, the volume and velocity of air currents are inversely propor- tional to the square root of their lengths. The quantity of air passing in airways of different areas is, other things equal, in proportion to the square root of the area multiplied by the area itself. The resistance varies directly as the length. The pressure required to propel air through airways is inversely proportional to the areas, other conditions remaining the same. The quantity of air circulating is proportional to the cube root of the power applied. Since the quantity of air circulating varies as the cube root of the power applied, and as the number of revolutions of a fan vary in the same ratio, it follows that the quantity of air circulating at any moment depends directly on the speed of the fan. Other general formulte, as arranged by Merivale, may here be given : — a. Ventilating pressure varies as depth of up-cast shaft (in furnace ventilation). h. Ventilating pressure varies as difference of temperature between up-cast and down-cast shafts. e. Ventilating pressure varies as horse-power of fan or furnace. d. Ventilating pressure varies as quantity of coal burned. e. Quantity of air circulating varies a^ revolutions of fan. /. Quantity of air circulating varies as square root of pressure. g, Quantitv of air circulating varies as square root of depth of up-cast (in furnace ventilation). h. Quantity of air circulating varies as dilfercnce of temperature between up- cast and down-cast shafts. y. Quantity of air circulating varies as cube root of horse-power. j. Quantity of air circulating varies as cube root of coals burned. ^Splitting' the Air, — The benefits to be derived by increasing the area of airways, and also by adding another airway, have been already pointed out. The latter method of solving this problem is termed ' splitting the air.' In former times (and even in some collieries at the present day) it was the practice to carry all the air round the workings in one current, which is a very bad method, and one that should be avoided if possible. The air should be taken round the workings in a number of separate currents, as only by this system can the greatest efficiency be obtained. Splitting the air, as already shown, increases the rubbing surface, but it reduces the velocity with the same pressure, and as the pressure varies as the rubbing surface and the velocity squared, a greater quantity of air can be propelled by a given power. There are other advantages gained by splitting the air, and venti- lating each section separately with main splits, among which are the following : — VENTILATION. 399 A greater total quantity of air is got. By splitting the air each section gets a more uniform and purer supply. A fall occurring in one split or section does not injure the others. An explosion taking place in one section is less liable to occasion disastrous effects in the other sections. Fewer trap-doors are required on the main roads. To obtain the greatest possible advantage from 'splitting,' the main splits ought to commence as near the down-cast and end as near the up-cast shafts as possible. In 'splitting/ the main current of air should never be split to such an extent that its velocity becomes insufficient to keep the working faces clear of gas. If this be the case, fire-damp or choke- damp may accumulate, and render the working-places dangerous. The velocity of the air travelling along the faces in fiery mines where unshielded lamps are used should never be less than 120 to 150 ft. per minute, nor more than 350 ft. per minute. In ordinary circumstances, the velocity along the face should be from 2 to 3^ ft. per second, in splits 3^ to 5 ft. per second, in main airways 5 to 10 ft. per second, and in shafts it often reaches 20 to 40 ft. per second. The relative proportion of air to be distributed among any given number of splits will depend greatly on the amount of natural gases given off, apart from the actual quantity required for men and animals, the burning of lamps and the blasting of explosives, so that in distributing a current it is best to divide it according to local circiunstances ; i.e. the section giving off the most gas should get the largest supply of air. The average quantity allowed by some authorities for mines free from fire-damp is 1 50 to 200 cub. ft. per minute per man and boy, and three to six times these quantities for each horse employed underground. In fiery collieries 200 to 350 cub. ft. per minute per man and boy ought to be allowed, and an additional quantity for 'scale,' as a certain proportion never reaches the working faces, being lost by leakage through defective stoppings, bratticing, and screens. The above quantities are only approximate. For A fiery mine employing 200 men and 20 horses, the quantity required would be : — men 200 x 350 = 70,000 cub. ft horses 20 x 2100 = 42,000 „ =11 2,000 cub. ft. per minute. Emud Splits, — The expression ' two equal splits ' means that the original single air-current has been divided into two currents, and each current traversing an airway of h/df the original length, but both with the same area as the originiQ one. * Equal splitting * is more of a theoretical than a practical expression, for to split an air current into two or more equal volumes can rarely be carried out in practice, although in some cases it may approximately be done. When the original single current is divided into two equal splits, they may be considered as one current with double the area, but with the same rubbing surface ; likewise, when divided into three equal splits, they may be considered as one with 400 PRACTICAL COAL-MINING. three times the original area bat with the same rubbing surface. This may be illustrated as follows : — Area. Rubbing Surface. Original airway, . 50 I jq. ft. 160,000 sq. ft Two equal splits. f 50 60 100 If f» 80,000 „ 80,000 „ 160,000 „ Three equal splits, 1 60 I 50 / 60 »» 53,333-3 ,, 63,333-3 „ 63,383-3 „ 150 It 160,000 „ EmmpU. ^If the total quantity of air passing round the workings of a mine is 20,000 cub. ft. per minute when the size of the airway is 8 ft x 6 ft. and 2500 ft long ; what quantity will circulate if the current is divided into 2, 3, and 4 equal splits ¥ First find the ventilating pressure required to circulate the original quantity through the given airway, by the formula / 20.000 \2 _A:^_'Q^^7x(26x2500x(j^^^^^) _ a 40 = 8 '8 lbs. per sq. ft. To find quantity with new area, v= / ^ ^ «?> ^ut p, k and s are the same in each instance, therefore the quantity passing in two equal splits will be as >/ai X aj : ^a^ xa^i : Q : x r»« ^^^ \/80 X 80 .-. 35 = 20,000-7——— V40 X 40 = 56,582 cub. ft i)er minute. The same result approximately may be arrived at by simply taking the nurob<*r ?t, of splits, thus s/lxl : 's/2x 2 :: 20,000 : x_ and y = 20,000^'^? IVl = 20,000x1-4142 = .'»6,568cub. ft. _ For three equal splits the quantity ar=20,000 ?V-^- 103,920 cub. ft IVI and for four equal splits the quantity x= 20,000 ^^ = 160,000 cub. ft IVl Unequal SplitUng. — This expression is used when an air current is split up into a number of 8e{)arate currents each of which traverses an airway of different dimensions and therefore meets with a varying amount of resistance. If there are a number of splits of unequal area, subject to a common pressure, the quantities of air that will pass in each are in ])roi>ortion to 1 -\ xS a V S VENTILATION. 401 where R= relative auantity of air passing into each airway. s= total ruboing surface in sq. ft. of each airway, a = area of each airway in sq. ft. Example,— kn airway 7 ft. x 9 ft. x 1200 ft , through which 80,000 cub. ft. per minute is {mssing, is divided into three unequal splits of the following dimensions : firHt split, 6 ft. X 7 ft. X 1200 ft. ; second split, 6 ft x 6 ft x 000 ft. ; third split, 6 ft. X 4 ft X 840 ft With the same total volume, what quantity will pass in each airway ? Let R], Kj, and R, denote the relative quantities going into each airway, then by the formula B,=/i^^, ^"" V (26 X 1200) V 31,!?00 ^"V (24x900) ~V21,600 * T,-,/ (6x4)» _^/i3:824_Q.j.Q ^- V -(20"^840) - V TmOO"^ ^^• These relative quantities show that for every 1*64 cub. ft going into the first split, 1*47 cub. ft. will be going into the second, and 0*90 cub. ft goinv into the tnird split. Let the total relative quantity be denoted by R4, then R4= Rj + Rq + R3 = 1*64 + 1*47 + 0*90 = 3*91 The total volume Xi going into the first split will be as R4 : Ri : : Q : arj 3*91 :1*64 : : 80,000 : arj ... xi=8^'^°^-^ii:54=81,608cub. ft. per minute. ' 3*91 For second split 8*91 :1*47 : : 80,000:81, . 80,000 X ^'^y^gQ Qyg.yg ^.^^ f^ minute. * 3*91 For third split 3*91 : 0-90 : : 80,000 : j-g 80,000x0*90^^3 ^Ig ^^l, f^ ^^„te. ' 3-91 ^ 31,508 + 30,076 + 18,416=80,000 cub. ft. The relative pressure or power required to pass the same Quantity of air through airways of varying area and length may oe found by the formal a S\a7 orSf-— j where A - area of roadways in sq, ft. S = ToUl rubbing surface in sq. ft. n- ,, ,, R = Relative quantity. 26 402 PRACTICAL COAL-MININa. too 80 212 Instruments used at Oollieries. — Thermometer. — A thermometer consists of a closed glass tube, with a capillary bore in the upper part, and a bulb below containing mercury or spirits of wine, and provided with a graduated scale having two fixed points, viz., freezing point and boiling point. There are three different kinds of thermo- metric scale adopted for recording the tempera- ture, viz., the Fahrenheit, Centigrade, and E^umur. R^umur divided the space between the freezing and boiling points into 80 equal parts, but there is no good reason why he should have preferred 80 over any other whole number. This scale is much used in Italy, Russia, and some parts of Germany. Celsius, a Swede, divided his thermometer scale into 100 equal parts between the boiling and freezing points : his scale is known as the Centigrade, and it is used in France and other countries of Europe, and is also being largely used in Britain among scientific men. In Fahrenheit's scale the space between freez- ing and boiling points is divided into 180 equal parts, and he fixed his freezing point 32* above zero. This scale is the one most commonly used in Britain. By the use of this instrument we are able to II measure the temperature of the air in the work- I ings, or note the difference in temperature iU between the air in the up-cast and down-cast H shafts. ■ The Barometer is an instrument used for I measuring the pressure of air. Its construction W is as follows : A glass tube 36 in. long, closed at one end, is filled with mercury and reversed, the open end being temporarily closed until it is placed so that it shall project below the surface of a bath of mercury contained in a reservoir. The barometer has a scale fixed to it, and also a sliding vernier, by means of which it may be read to the one-hundredth part of an inch. Each inch on the scale is divided into tenths, and the divisions on the vernier are one less than the number on a corresponding length on the barometer scale. A barometer is of great use at collieries, as it shows the changes in atmospheric pressure. With a low barometer the gas issues more freely from the coal, and if there is any gas lying in the waste it will soon find its way into the working places, owing to the reduced 32 01 Fio. 487. ■5 YKNTILAnON. 403 r fall of the preasuro. It is important, therefore, to note the rise o mercury daily in connection with fiery collieries. By the Coal Mines Regulation Act every mine must be provided with a barometer and a thermometer. The reading of the former should be noted at least once a day, especially by the firemen before going down to inspect the workings in the morning. Waier-Gauffe. — A current oF air exerts a certain pressure during its passage from one point to another, which pressure is usually measured by a water-gauge (fig. 438). The construction of this instrument is very simple. It consists of a glass U-tube, of J in. to 1 in. in diameter, to which a sliding scale divided into inches and tenths is attached. One of the ends is fitted with a tube at a right angle with the limb, which can pass into the intake through a screen, while the other end is connected with the return current. If there is any difference in the pressure between the two currents the water level in the two limbs of the gauge will vary. As 1 cub. ft. of water weighs 625 lbs., a cub. in. will weigh 036 lb. In a tube of 1 in. sectional area, a difference of level of 1 in. will repre- sent a wind pressure equal to the weight of 1 cub. in., and, pari patmt, to '036 lb. per sq. in., or -036x144 = 5-2 lbs. (approximately) per sq. Ft. The water-gauge thus acts as a check (though not altogether a very reliable one) on the state of the underground airways. If the latter remain in the same condition for some time, and the ventilating power is neither increased nor decreased, then under ordinaiy circumstances the height of the water-gauge ehould not vary. If the dilfcrence in level is very much greater than usual, it will probably be due to the fact that the air is not taking its usual courae, owing to some doors being open in the main airways, by which the air will be going direct from the down-cast to the up-cast without ventilating the workings. If the water-gauge is to be of any use at all, it ought to be placed as far back from the fan as possible, otherwise it will be Fio. 438.— Wster-gangfl. 404 PRACTICAL COAL-MDJIKO. impOBsible to get correct results, owing to the abnormal condition of the air close to the fan. HygTOmeter. — The amount of moisture in the air can be ascertained by the use of the instrument known as the hygrometer. It consists of two thermometers (fig. 439) mounted at a short distance from each other, the bulb of oue being covered with muslin, which is kept moist by means of a cotton wick dipping into a vessel of water. The evapo- ration which takes place from the moistened bulb produces a depres- sion of temperature, bo that this thermometer gives a lower reading than the other by an amoimt which increases with the moisture of the air. The instrument must be mounted in such a way that the air can circulate freely round the wet bulb. By means of a formula,* the tension due to the vapour of water in the air is calculated from ^10 readings of tlie two thermometers. Tables have also been coustructed, by means of which the degree of saturation can l)e calculated. Anemometei-s. — To determine the velocity of the air passing in undergrouDd workings, it is the common practice to use the instru- ment called the anemometer. It is con- structed somewhat like a small fan, with a number of blades or vanes fixed obliquely to the asis (see figs. 440, 441); when these vanes are rotated a clockwork gearing con- nected to the axis, which actuates the pnintera on the dial of the instrument, records, by means of a scale, the velocity in feet at which the air is travelling. In determining the quantity of air passing, the pointers are first brought to zero, and the anemometer is held out at arm's length in the air passage for a Fio. 439,— Hygrometer. measured period of time, and a rending is taken, the hundreds being read off the small pointer, and the odd feet read off the large one. The sectional area of the passage is carefully calculated, and the total quantity of air passing can be ascertained by multiplying the velocity per minute by the area in sq. ft. Goal-Ihut and Kethods of dealing with it. — That coal-dust is an important clement in connection with explosions in underground workings seems to be fnlly recognised by all or nearly all connected with mining operations. It is niany years since this fact was first pointed out and experiments made by two eminent authorities, Faraday and Lyell. It is over fifty years ago since these distiii- * See DeBchsnera JfatUTal Fkilosophy, p. 39S. VENTILATION. 405 guiuhed men first gave their opinion un thiu uinuli-dobtited question, but it is only within recent years that much attention huH been given to the subject. To Mr William Galloway and the late Sir Frederick Abel we are greatly ludebted for the information ne posseBs on the ttubject. These two authorities studied the question very cloeely for years, and after many carefnl and comprehcnaive experiments, came to the conclusion that "coal-dust is highly dungcronit under certain conditions." Othem have entered the field of investigation, and the results have placed beyond doubt the stAtement that coal-dust, rather than fire-damp, plays the most important part in many colliery explosions. There are two theories held by mining authorities regarding the action of coal-dust in colliery explosions, one being that coal-dust alone will cause an explosion without any fire-damp being present in FioR. 440, 441.— Anemometer. the air, and the other, that before coal-dust becomes reully dangerous a certain percentage of fire-damp must be present in the air. We may here quote briefly the opinion of diff'erent authorities who were commissioned to make inquiry on the subject. MM. Mallard and Le Chatelier of the French Fire-d^mp Commission of 1882 rejected the theory that coal-dust alone would cause any serious danger, or tliat any colliery explosion of importance could be attributed, with any probability of authenticity, to the action of coal-dust. The Prussian Fire-damp Commission in 1887 came to the con- clusion that the presence of coal-dust in the complete absence of fire- damp gave rise generally to an elongation or propagation of the flame projected by a blown-out shot of limited eitent, however far the deposits of duat may extend in the mine roads, but that there were certain descriptions of coal-dust which, it ignited by a blown-out shot, 406 PRAGTIGAL GOAL-MIKING. would not only continue to carry on the flame, even to distances much beyond the confines of the dust deposits, but would also, in the entire absence of fire-damp, give rise to explosive results, which, in character and effects, were similar to those produced with some other dusts in air containing 7 per cent, of fire-damp.* The Austrian Fire-damp Commission in 1891, after making a large number of experiments with different coal-dusts, found that, in the absence of fire-damp, nearly all kinds of coal-dust could be ignited by a 3^oz. dynamite cartridge exploded in an unconfined space, while many dusts which were notoriously regarded as dangerous provev/-«- = \/ -r = 1 = relative quantity in ar, and R= w -^ = '447 = relative quantity in y. The actual quantities passing into x and y will therefore be found by pro- portion, thus 1-447 : '447 : : 10000 : y='^*^,^l^»?^-^=3089a6 cub. ft. per minute, 1*447 and ic=10,000 - 30S9-15 = 6910'86 cub. ft. per minute. VENTILATION. 413 Example, — Find the total quantity of air per minute passing in an airway 10 ft. X 7 ft. X 2000 ft., at a pressure of 8'5 lbs. per sq. ft. PA = KStr«. Here P= 8 -6 lbs. ; A = 70sq. ft. ; Per=34 ; 8 = 34x2000; ^=(,qq? .) 8-6 X 70= -01 X 84 x 2000 x d» 595 = 680«» 596 .'. tr»=ggQ; and i?=V8760= -9364, and Q the total quantity = *9854 x 1000 x 70 = 65,478 cub. ft. per minute. Example. — If the quantity of air passing round a mine is 10,000 cub. ft per minute before splitting, when the size of airway is 6 ft. x 5 ft. x 1200 ft. long, what quantity will circulate if the current is split respectively into two, three, and four equal {larts, the pressure and other conaitions remaining the same ) Here the pressure and rubbing surface ^11 be the same in each case, therefore the quantity will vaxy as ^/Ag or Qn= V'l x n x Q. (1) Qnj = V^^x 2 X 10,000=28,280 cub. ft. in two equal splits. (2) Qn,= V3 X 3 X 10,000 = 61,930 cub. ft. in three equal splits. (3) Q7i,= V^ X 4 X 10,000 = 80,000 cub. ft. in four equal splits. Example, — ^A down-cast shaft, 14 ft. diameter and at a temperature of 50" F., passes 121,000 cub. ft. per minute. What size of shaft would the up-cast require to be, if the velocity of air current in both shafts is to be equal, supposing the temperature in the up-cast is 100** F. ? Velocity in down.cast=^ = -i^i^^ = 786-1 ft. per minute. Increase of volume in up.ca8t=^'^-^=^— »?^-?^^=13,180-82 cub. ft *^ 459 469 .-. total volume in up-cast= 121,000 + 13,180*82= 134,180*82 cub. ft. A f 4. Q 134,180*82 ,-A.«o-« ft. and area of up-cast = -i?- = — J^ttt^- =170 '69 sq. ft ^ V 786*1 ^ .*. diameterofup-cast=>v/^^^'- =14*74 ft. ^ V -7854 Example,— -'^o shafts, each 15 ft x 6 ft x 100 fnis. deep, are connected by a drift 11 ft x 5 ft. x 400^ yds. long, the quantity of air passing being 80,000 cub. ft per minute. Find the quantity that would pass if another drift were added 11 ft X 5 ft X 400 yds. long, (1) with same pressure, (2) with same horse-power t (1) The pressure required will be the same for each shaft NowPxA=KxSx«» .•.Pxl6x6 = -01x40x600x(^30-0^J .-. P=*01x8x40x (^\ =*51 lb. persq. ft. and the pressure in each shaft = *51 x 2=1*02 lbs. (2) Find pressure in drift. Px56 = '01 x32x 1200x^ J^^'^^^^V P X 11 X 121 = -01 X 32 X 240 x 36 ... P=-01x32x240x36^2*071bs. persq. ft 11 X 121 ^ ^ 414 PRACTICAL COAL-MINING. If another drift of the same size were added, the velocity would be halved, and 2*07 therefore would only require i the pressure and — — = *517 lb. to pass 15,000 4 cub. ft. in each airway. Pressure in shaft and drift before splitting r= 2 '07 x 1 "02 = 3 '09 lbs. , , after adding an additional airway = 1 *02 x '517 = 1 '587 lbs. Now quantity oo ^/pressure. . •. ^Jl-bSf : »JS'09 : : 80,000 cub. ft. .•. 1-23 : 175 : : 30,000 : x and aj=??»M^l:Z? = 42,482-92 cub. ft. per minute (when the second drift is 1 *2u added). H.P. before adding airway = ?2i^?^^'il^^= 2 -8 * ^ 33,000 after _42,482-92x 1-537 _,. 97 » after „ „ - 33 q^^- - -197. Xxample,—U the difference in temperature between the up-cast and down-cast shafts is increased four times, how is the pressure and quantity altered ? (1) The pressure varies as the difference of temperature between the up-cast and down-cast, so if the latter increases four times, the pressure will also be in- creased four times. (2) The quantity varies as ^difference of temperature between the two shafts. Therefore increasing the temperature four times increases the quantity by the ^4 = twice. OHAPTEB XIV. SAFETY LAMPS. It is now over eighty years since Sir Humphry Davy crowned his long and patient researches by the invention of his safety lamp, an event which marked a new epoch in coal-mining. Before Davy's time the miner had to rely on very insecure methods for detecting or for working in the presence of fire-damp. At the beginning of this century Spedding's steel mill was the only apparatus which enabled him to continue his work in the presence of small accumulations of gas. By this machine, which was soon demonstrated to be unsafe^ and which was the cause of numberless explosions, the miner was en- abled to work by the faint light of an intermittent spark resulting from the contact of a piece of flint with a revolving steel disc. Since the introduction of the Davy lamp, large numbers of other safety lamps have been patented, but all are on practically the same principle as Sir Humphry Davy's, although some are, of course, a great improvement on the original, both as regards safety and lighting power. Deflniiian. — " Safety lamps are contrivances by which a light, sur^ rounded by an explosive mixture of fire>damp and air, may be main- tained in lamps without communicating flame to the outside atmos- phere." As at present constructed, they depend upon the fact that flame, when brought in contact with wire gauze of certain degrees of fineness, cannot pass through it, owing to the rapidity with which the heat is conducted away, so that it cannot be communicated to the outside atmosphere. Sir Humphry Davy first demonstrated this by some experiments he made with metallic tubes. He found that it was easy enough to eflect an explosion of fire-damp and air in a wide vessel, but that it was impossible to effect it in a narrow metallic tube. Metallic tubes of ^ of an inch in diameter and 1 J inches long pre- vented an explosion, and this phenomenon, according to' Davy, probably depended " upon the heat lost during the explosion in contact with so great a cooling surface, which brings the temperature of the first 416 PRACTICAL COAL-MINING. portions exploded below that required for the firing of the other portions ; and it has been already shown that the fire-damp requires a very strong heat for its inflammation. Mixture of the gas with air I found, likewise, would not explode in metallic canals or troughs, when their diameter was ^ of an inch., and their depth considerable in proportion to their diameter, nor could explosions be made to pass through such canals. Explosions, likewise, I found would not pass through very fine wire sieves or wire gauze." Now wire gauze is nothing more than a series of small tubes, having very small diameters, and of very short lengths. The wire gauze mostly used for safety lamps has 784 apertures to the sq. in. Davy Lamp. — This lamp, as originally con- structed, consisted of a small cylindrical vessel b for holding the wick and oil, provided at the bottom with a pricker/ for trimming the former, and surmoimted by a cylinder of wire gauze a, made double at the top, and supported by small iron rods c, terminating in the cover dy to which is attached a handle. The gauze cylinder is about 1^ in. diii meter, and 7 in. long, with wires about ^^ of an inch in diameter, having, as already stated, about 784 openings per sq. in., through which air enters to keep the flame burning freely. If a certain percentage of fire-damp enters along with the air, the mixture will ignite and fill the space inside the gauze with flame ; but as soon as this flame comes into contact with the wire gauze, it is immediately cooled down, and cannot pass through the opening unless it is allowed to bum until the gauze becomes heated to a certain temperature, when the flame can pass through to the outside. An explosion may be brought about by a * Davy ' lamp in several ways, such as : — By allowing gas to bum inside until the gauze becomes red hot. By allowing a strong current of air to blow against the lamp, thua forcing the flame through the gauze, which occurs when the air attains a velocity of about 5 ft. per second. By a sudden jerk or shock to the lamp, or by a shock due to heavy blasting operations. By the miner carelessly damaging his lamp or opening it in the presence of an explosive mixture. The great disadvantage of the * Davy ' lamp is the very poor light that it gives, ^ to -^j^ of a candle power only. The * Davy ' lamp in its original form is little used now, being unsafe in most collieries, where the air now travels at such high velocities round the workings. Clanny Lamp, — This lamp is similar to the * Davy ' lamp in con- Fio. 444.— Davy Lamp. SATBTT LAMPS. 417 stniction, but has a glass oj'linder a instead of the lower portion of the gauze, which enables it to g^ve a much better light, and to be more eaeilj oairied in an air current; but, on the other hand, it oauses an explosion more readily, owing to the area of gauze cylinder being smaller than in a 'Davy.' It is also unsafe in a very strong current of air, as it will readily pass the flame when the air is travelling at a velocity of 6 or 7 ft. per second. This lamp is not now used unless it has an additional proteotion in the shape of an iron shield sur- rounding the outside of the gauze. Stephenion Lamp. — The essential points of dissimilarity between a 'Davy' lamp and a 'Stephenson' lamp are that, whereas in the fonner the flame is simply surrounded by a wire gauze through Fis. UB,— Olum; Lamp. Fio. 446.— StfphenBon Lump. which the air passes, in the latter the flame Is surrounded and bums within a glass cylinder a, covered at the top with a perforated copper cap b, and is fed by air passing through perforations in a metal ring e at the bottom. The lamp has in addition the wire gauze of the 'Davy,' and if the glass happens to get broken it still remains safe. IJke the 'Davy,' the 'Stephenson' lamp has a very small illum- inating power, and is very readily extinguished, but is very much safer than the fonner in air currents, as it will not ' pass ' the flame until the velocity of the air reaches 8 to 10 ft. per second. This lamp is now little, if at all, used in fiery mines. MartaiU Lamp. — The 'Uarsaut' lamp, which was the invention of a well-known French mining engineer, differs very little from the 'Clanny' lamp. Instead of having a single gauze like the 27 418 PBAOnOAL COAL-MINISQ. ' Clanny,' it is provided witb two or tliree gauiea fitted into tlte ineidc of each other, which tends greatly to increase the safety of the lamp. Ab used in Britain it is made with two g&uiee only, with the addition of an iron Bhteld as a further protection, and in this form it is a very safe kind of lamp for use in fiery mines. The Marsaut lamp is largely used both in England and Scot- land, and has much to recommend it, as it doee not pass the flame until a very high velocity of air current is reaehed, and it has the further advantage of not being so oaaily ezUnguished as some other forms of safety lumps. For onoast men eepecially, such as roadamen, pony-drivers, etc., die Marsaut is to be recommended, as the nature of work those persons are engaged in varies greatly from that of Fio. 447 —Haranut Lamp. Fto. 44B.— MaMelwLainp, a miner working at the coalface, where a lamp is used under more &vourable circumstances, being in most cases kept perfectly still or at most moved about only over small areas. In collieries where there is only a small amount of fire-damp given off, this lamp is often used without the outer shield, and with only two gauzes, which makes it much better suited for underground requirements, as the amount of light given out is much increased by the freer supply of air that the fiame receives, and the latter is not so eaaity ex- tinguished as when the shield is used. Muetder Lamp. — The Mueselcr lamp is constructed somewhat like the Marsaut It has the glaas cylinder round the flame in the same way, hut instead of having two or three gauzes it has a single g:uizo only, with a conical -shaped metal chimney a (fig, 448) (1) It ij (2) The SAFETY LAMPS. 419 fitted inside, immediately above the glass cylinder, to which it is fixed by a ring of ganze b. The air to feed the flame passes first through the outer gauze, then through the gauze cap between the metal chimney and the glass to the flame, and the products of combustion pass up the metal chimney through the gauze cylinder and into the atmosphere. The metal chimney has thus a double purpose to serve, viz., to create a strong upward draught and to insure the inlet air being drawn down close to the glass to keep it cool. When fire- damp is suddenly ignited in this lamp the resulting gases, principally COj, fill up the conical chimney and speedily extinguish the flame. The great drawback to this lamp is the readiness with which the light- is extinguished, it being very sensitive to the least shock or jerk, while, if held slightly out of the perpendicular, the light at once goes out through the supply of air being cut oflf. Nevertheless, it is exten- sively used both in Britain and in other European countries, and is both good and safe where there is plenty of ventilation. The Royal Commissioners on Accidents in Mines objected to this lamp on the following grounds :— is very easily put out. The glass is easily broken by a blow, by the flame playing on it, or by cold water coming in contact with the hot glass. (3) There are difficulties in getting tight joints where the metal ring and glass cylinder meet. (4) Difficulties arise from combustion with a tendency to smoke the glass, thus lowering the illuminating power. These objections might also be urged against nearly all the safety lamps at present in use. Hepplewhite-Oray Lamp, — In this lamp and its newer modifications, the construction differs somewhat from any other safety lamp ; the differences consisting chiefly of the manner the air is admitted to feed the flame, and also in the shape of the glass cylinder surrounding the latter (fig. 449). The standards for supporting the lamp^ instead of being solid, as they are in other lamps, are made of tubes down which the air passes to an annular chamber, situated immediately over the oil vessel, and protected by wire gauze. In the form in which this lamp is now made, there are only three inlet tubes instead of four as formerly, one of the tubes being considerably broader than the others and acting as a deflector. The glass surrounding the flame, instead of being cylindrical in shape, is made in the form of a cone, and is very much longer than the glass of an ordinary safety lamp. Imntediately above the glass is a gauze, also of conical shape, and outside that a cone of metal, the whole forming a very strong compact lamp. In addition it is fitted with a shut-off arrangement, so that the air can be admitted either at the top or bottom of the tubes. In the new form a shield-plate a a, which is part of the hood, projects over and completely covers 420 PRACTICAL COAL-MINING. the top of the inlet tubes, and prevents the lamp from being ex- tinguished as readily as the older type. The air passes down the tubes, while the products of combustion pass upwards and out into the atmosphere by two horizontal rows of holes bb, in the hood c. To facilitate the cleaning of the lamp, the ring securing the glass is screwed on to a vertical plate d, which forms the air inlet. This arrangement enables the whole of the inside to be quickly and easily removed when the lower gauze ring is unscrewed. It is claimed for this lamp that it gives a much superior light to any other form, owing to the shape of the glass, which allows the rays of light to be projected in all directions, thus permitting the roof to be examined with ease without tilting the lamp. It is also claimed for it that very small quantities of gas can be readily detected by its means. The author has had little practical experience of this lamp, but some time ago some prac- tical firemen and overmen, who were attending a class in Lanarkshire to which he was lecturing, mostly made, under his directions, a num- ber of tests with the Gray lamp, and at the same time with Mueseler and Marsaut ^.v:--^^-/.:;vv-v:S::,>:;i^/,;.^l ' *^^La*<^ lamps ; and reported Y\g. 449.— Hepple white- Fig 460.— Wolf Lamp, that the former could Gray Lamp. be used to detect small quantities of gas much more easily and quickly than either of the others. The only objections to the use of the Gray lamp are its weight and expensivcness, but there can be little doubt that it is a very superior lamp for use underground. It is very safe in every respect and can withstand almost any current of air met with in collieries, having been tested with velocities up to 100 ft. per second without passing the flame. Wolf Safety Lamp.— This safety lamp, constructed to bum benzine, is very largely used on the Continent. It is soniewhat similar to an ordinary Marsaut lamp, with two gauzes, and is pro- vided with a corrugated shield, provided with apertures, which is said to give it additional safety and allows of its burning more freely. It is also provided with an * igniter' for relighting it if extin- SAFBTT LAMPS. 421 guishcd, without rendering it necessary to unscrew the bottom of the lamp, which is a great advantage. The fastening is secured by a magnetic lock, and cannot be opened without the aid of a powerful magnet. It is said to give a much better light than an ordinary safety lamp burning oil, and can withstand strong air currents, and detect small per- centages of gas, while the cost of fuel is low compared with other lamps. Wolf'Dahhnann Lamp, — This may be said to be an improved Wolf lamp. In it the air is con- ducted from above the flame through a gauze ring 1^ ins. in height which is covered by a movable brass cylinder. The pro- ducts of combustion are carried off by an inner brass cylinder, at the top of which is fixed a wider cylinder (see fig. 445), the latter being capped with wire gauze. Inside the inner brass cylinder is a gauze chimney, so arranged that it can be taken out for the purposes of cleaning. By means of this simple arrange- ment the products of combustion rapidly pass off, while fresh air enters from all sides through the gauze to the flame without becom- ing mixed with the products of combustion. In this manner a good circulation results, which causes the flame to bum steadily and brightly, while it is easy to light the lamp while locked by means of the igniter which i** placed within it. * Evan Evan's Lamp. — This is a J^ bonneted Clanny lamp, with the Fio. 451.— Wolf-DahlniAnn Lamp. bonnet, which extends from the flange above the glass to the dome of the lamp case, fixed permanently. The air is admitted through a series of holes in the horizontal flange above the glass. The products * EspoH of Boyal Committion on Accidents in Mincf!, p. 206. 422 PRACTICAL COAL-MININQ. of combustion esc&pe through a series of holes in the top of the bonnet (see tig. 452). This kinp is also provided with an autoroaUc arrangement for closing it in the event of gas becoming ignited in- side the gauze, the main features of thia arrangement being as follows '■ — Within the bonnet and surrounding the gauze are two cylinders of the snme height closely Gtting one another. The inner cylinder is open at the top and is perforated near the bottom with fifteen holes, each J in. in diameter. The outer cylinder, which is closed at the top, is perforated near the top, with a similar series of holes. A rod slides tlirough a tube and is maintained in position by a loop of thread close to the gauze and stretched belween two hooks. If th^ loop gets burned through, by gas burning inside, the rud is Fto. 452.— Evan Evuu'e Lauip. Hg. iiS.—Kvun Tlioniiw Lsui{i. no longer lield in pusitiiju, and a strong spiral spring between the top of the outer cylinder and the dome of the lamp pushes the former down over the inner cylinder, and thus closes Ixith series of holes simultaneously, and extinguishes the flame in a few seconds. f'van Tliomas Lamp. — Tiiis was one of the lamps which was tested by the Mines Commission, and reported upon as giving very satisfac- tory results. In its principles and construction it is an improved form of the Claiiny lamp. At the bottom of the gauze cylinder is a close fitting brass ring or tube about 1 in. high, the top of the ring terminating in a horizontal flange, which extends to within about -^ of an inch of the outaide shield or bonnet. Through this small space the ink-t air is admitted to feed the flame, the produota of combustion passing out at the top of the bonnet. SAFETY LAMPS. 423 The Evan Thomas lamp is simple in construction, gives a fairly good light, and is safe in currents of air travelling with a velocity of over 50 ft per second. It has also the advantage of not being veiy readily extinguished by a sudden jerk or by being held on the slant. In an explosive atmosphere, however, it soon becomes extinguished. The following table of experiments with safety lamps in currents of air of different velocities is interesting, as it shows the behaviour of different lamps and the ratio of safety under these conditions. Percentage of Velocity of jy .--Hq-. ^e Name of Lamp. Gas present Air in ft per R™-;nienL Results, in AiF, fninntA i»x penmen u Davy lamp, . •I II m air. minute. per cent 600 10 seconde. Ezplosioii. II 400 60 „ „ „ 870 180 ,, No explosion. 800 60 II "v^ "V II II 1600 60 „ „ Davy (sbielded), . „ (in can), . Stephenson lamp safe up to 800 ft per minute. Clannv „ „ 600 „ „ Mueseler lamp, . 8 per cent 2888 5 „ Lamp went out „ ,,. .13 ,, 2888 76 ,, Crontinued to burn. . IS „ 600 6 „ Explosion. II II The Marsaut lamp gave the same results as the Mueseler, but it was foimd that if the current of air was reversed while being admitted to the flame, an explosion occurred in 5 seconds. The number of safety lamps that have been patented and placed on the market is so large that it would take a large volume to fully describe them all. One writer enumerates over seventy, and that by no means exhausts the list Fire-damp Indicators, — Within the last few years a large number of instruments for detecting small percentages of fire-damp have been brought before the mining public, but very few of them are of much practical use to the miner, most of them being too complicated in design, too sensitive to be handled freely, and too expensive. Hydrogen Indicator, — It has long been known that the pale hot flame of hydrogen gas is very sensitive to the presence of fire-damp, even when the latter is present in very small quantities. Professor Clowes has invented a lamp in which a hydrogen flame is used for the detection of small percentages of CH^. The accompanying figure (454) shows this apparatus as used in conjunction with an ordinary Heppelwhite-Gray- safety lamp. A small cylinder C, con- taining hydrogen at very high pressure, is attached to the lamp, and at the bottom of the cylinder a tube B, of small diameter, is con- nected with the interior of the safety lamp, the top of the tube being just about on a level with the burning wick W. When a test is to be made, hydrogen is admitted through the small tube B, by opening a tap T, with a key. The flame of the ordinary wick inunediately lights the hydrogen, the jet of which can be regulated to any re- quired siie of flame. The ordinary wick is then drawn down by 424 PHACnCAL COAL-MINIKG. meana of the pricker, aod the large flame being extinguish ed, the iadicator ia ready to make a test with the hydrogen flame alone. A Bmalt ladder-like ecale S is fixed inside beside the flame, to measure the percentage of gaa found, each of the steps on the scale being a definito value. The lamp is guaranteed to measure as little as 025 per cent, of fire-damp in air. The small hydrogen cylinder can be detached and carried in the pocket when not required for testing, and the safety lamp can then be used in the ordinary way. Stoked Indicator. — In this lamp 'absolute alcohol' is employed to produce a flame for detecting the presence of small quantities of fire-damp. The indicator may be used with any ordinaiy safety lamp, and is a very simple arrangement, shown in fig. 456. A small vessel 6 e, having a thin tube and wick, screws into an opening at the bottom of the safety lamp, the top of this tube reaching Fto. 154.— Hj-drogen Indiwtor. FiOi 4GC.— Sh>k«a' Indicatoi. to the top of the wiok a, where it oon be lighted ; a slit i, at the top of the alcohol tube gives the standard flame for testing. WhoD a teat is about to be made, the brass plug c, which fits the opening at the bottom of the lamp, is unscrewed, and the tube of the indicar tor inserted. In a few seconds the heat will cause the alcohol to ascend and ignite at the oil flame. The oil wick is then drawn down ' illar, the candle and the amp being each in a cylinder of white tracing paper 2 ft high and 8 In. diameter. 26 (average) II II II II II ' I II If •• 5 (average) 23 .. flame average height, . . i\ Deflector lamp, large flat flame, 3 ,, „ moderate clear, 5 CI iffbrd lam p, very good flame, 1 1>\, ,, „ moderate flame, 2} AsUworth lamp, ... 3^ Stephenson lamp, good flame, 7^ Tallow caudle, good average flame, . . • • !{ The light of safety lamps will depend a good deal on the sort of oil used and the state of the ventilation ; light oils, such as petroleum and colzaline, giving a much better aud clearer light than heavy oils, such as rape or seal oil. If light oils are used, they require to be very carefully handled, and no naked lights brought near the oil receiver, as they give off inflammable gases at comparatively low temperatures, and are apt to catch fire very readily and do much damage. The writer has known at least half-a-dozen cases where lamp rooms have been set on fire aud destroyed through careless handling of these light oils. The Royal Commission on Accidents in Mines recommended a mixture of vegetable or animal oil with about one-half its volume of a petroleum oil of safe flashing point, as giving the best results as an iUuminant for safety lamps. Cost of Upkeep of Lamps, — The average cost of safety lamps — if used with light oils, which are cheaper than the heavy vegetable oils, — including both oil and wick, is about a halfpenny per lamp per shift. Thus Davy lamps cost about 0'375d. per day for oil alone ; Mueseler lamps about 0*295d. ; while the cost of naked lights may be estimated at l'25d. per diem. The following is a detailed statement of the cost of safety lamps per annum, as ascertained at the Clyde Collieries, Hamilton, although the writer thinks that some of the items, such as gauzes and glasses, are underestimated : — Cost of oil (800 days) per lump, . . • Repairs, „ ,, Gauzes and glasses (300 days) per lamp, . Lampmen's wages, ,, „ Total cost, . 8. d. 7 *i 0 a 0 2i 9 3i IL Ji BAFKTT LAMPS. 429 Locking Contrivaneea. — Nothing conduces more to the safety of a lamp, or of those using it, than an efBcient method of locking ; for if the cause of taaay eiplosions could be accurately ascertained, it would be found that not a few of them were caused by miners them- aeWea surreptitiouBly opening their lamps; indeed, in many explo- sions, this has been clearly ascertained to have caiised the disaster. It is a notorious fact that few men are more careless of their own safety than miners, who have been known to open their lamps at the face, even in the neighbourhood of large quantities of fire-damp. In the old method of locking lamps, a padlock was often used, and could be opened easily by a duplicate or skeleton key. Another louk which was largely us^, and is still used to some extent, was a small screw bolt, either with a square or tapered head, which was turned until the body of the lamp and the bottom were fastened to- gether, by means of the bolt pinching the bottom part. This lock was of little use, as any workman with an old nail filed to the proper size could open his lamp by unscrewing the lock. The simplest and beet method of looking a lamp is by using a nveted lead plug, con- necting the body of the lamp with the oil-vessel. The lead ping should be firmly riveted, and each end stamped with letters or marks, varied from day to day. Without this precaution it has been found that the rivets can be removed and replaced in such a way as to render detection extremely difficult. Jfagnetic locks are also used, in which the lamp can only be opened by the aid of a powerful mi^net. Of this class. Wolfs mi^- netic lock is the simplest and most satisfactory. Protector Lock. — Many lamps are now fitted with the ' Protector ' ■rt ' - J M y» arrangement for securing the oil- Jir^ciiiK new «tf O-O' yQ^ael to the top part of the lamp. ax^ vO Iq addition to this arrangement the lamp is sho locked in the usual way. The apparatus will be understood from figs. 469, 460. The wick-tube has a screw thread upon it through' out its whole length, and on this is screwed a 'thimble' aa, provided at its lowor end with a flange, on the outer end of which a screw-thread is also cut By the latter screw the FiQ8.459,«0.-'Protector'Lock. oil-cup is attached to the lamp, and, when this has been done, the flanged thimble is fastened in position by a bolt h, provided with a spring; the bolt cannot, therefore, be withdrawn until the oil-cup is removed. The thimble is screwed on to the wick-tubc ^^ 430 PBACTICAL COAL-MINING. before the wick is lighted. The oil-veesel can, of course, be readily removed, but only by making the end of the wick-tube traverse the closely-fitting thimble above mentioned for a distance of 1 to r5 in., and during this process the diminished flame of the naphtha spirit is certain to be extinguished. With this arrangement it is practically impossible to open the lamp without extinguishing the flame, unless the lock bolt gets broken or the spring attached gets out of order, which does not readily happen with fair treatment. As already stated, the oil-vessel is fastened in the ordinary method by riveting with a lead plug, which gives additional security, and also permits the oil-vessel to be partially unscrewed for the purpose of regulating the flame, but prevents it from being altogether withdrawn. Testing Lamps. — All safety lamps, before being taken into the mine, require to be tested at the lamp station on the surface, or at a station at the bottom of the shaft, to see that they are in a safe condition for using, and also to ascertain that the parts are properly fitted together, particularly the glass and the connecting parts at the top and bottom of it, for it is absolutely essential to safety that no opening should be left at the junction of the glass with the brass rings for an explosive mixture to entor the lamp and ignite at the flame. The testing of the lamps is often done in a very cursory way at many collieries, owing, no doubt, to the lamp attendant not being aware of the true value of such testing. The simplest method of testing safety lamps is to take a brass tube of small diameter, somewhat like a blow-pipe, and to blow through it with the mouth so that a current of air impinges against the glass all round the top and bottom edges. If the glass is not properly fitted, it will be detected by the current of air getting in at the edges and deflecting the flame or extinguishing it altogether. Sometimes the lamps are tested in a more scientific manner by being inserted in an inflammable mixture to see if they are really 'safe,' this method being much better than the blow-pipe test. * A testing apparatus for safety lamps is shown in fig. 461. A and B are two cylinders which fit into one another. The cylinder A is filled with water to about three-fourths of its capacity, and the cylinder B, the bottom of which is open, contains a valve at the top of it. By simple pressure of the thumb, the valve can be opened, whereupon cylinder B is made to rise to three-fourths of its height, and become filled with air. At the bottom of the cylinder A is a pipe, which, as it extends above the surface of the water, receives the air that cylinder B forces into the reservoir C, where the gases are generated. C is a reservoir, the inside of which is divided by several partitions, made of corrugated iron, and filled with some absorbent material such as cotton wool. The glass cylinder D is filled with benzine immediately before the apparatus is required for * The author is indebted to the makeni, Messrs FrieTnnnn k Wolf, for the diagram and description of this apparatns. SAFBTT LAMPS. 431 use. If the cock £ be opened, the benzine will flow into the reservoir C, in which it is obliged to follow the windings of the sheet iron, and in this maunei offers a Ini^ surface to the air, the latter being thus impregnated with benzine and transformed into gas. The gas then pnsaes through the cock F into the testing cjlinder O, which is made of tin-plate, and fitted with a pane of glass. Inside this t«sting cylinder there is a spiral pipe, the inside of which is drilled with small holes which serve for the admission of air. By means of a metal sliding valve the quantity of air entering may be regulated. The lighted lamp is placed within the spiral pipe in the Flo. 401.— Teating App«ratiu for S&rety lAinps, cylinder G, and the cock F is opened. The gas issues through the fine holes in the pipe and streams on to ibe lamp. If the latter be defective, the generated gas will be ignited in the cylinder G, but the flame of a well-Gttcd lamp will be extinguished in the presence of too large a quantity of this gas, which will produce the same effect upon the flame as fire-damp does. To make more elaborate tests of safety lamps in explosive gases, a larger and more costly apparatus may be employed. The apparatus will be understood from tig. 462. It couBists of a tank A, surrounded by water like an ordinary gasholder. Connected to tbis tank are two pipes C and D, of 2 in. diameter. The pipe C ia connected to the month of a Iour wooden boi B, about 2C ft. lonp, I0| in. high, and 4 J in. wide, conatrncted of boards 1^ in. thick, carefully 432 PBACnCAL COAL-MINING. jointed together, with all cracks or seams completely closed. On the top of this hox, and at distances of 2| ft. apart, are openings which are closed with covers H H, which are easily displaced by any explosion of gas which may occur in the box, and permit the exploded gas to escape. To produce changes in the direction of the current of mixed gases from the horizontal, upward or downwaid, according as it may be desired that the gas should impinge upon the burning lamp, arrange- ments have been made to adjust the lamps inside to different levels (see fig. 462). In order to make the necessary observations on the conduct of the lamps during the test, a part of the wooden box is inclosed by a wooden partition I, in such a way as to entirely darken it, and enable the observation of every change in the flame of the safety lamp to be made. The somewhat dangerous observation of the safety lamp BDark c cbMmber / H ' Ossholder cjtpac/ty i3/ cub ft Fio. 462. — Special Testing Apparatus. during a test is made through a glass plate ^ in. thick, which is set in the door through which the lamp is placed in the box. The velocity of the air current or gas mixture, which can be increased up to 59 ft. per second, is produced by means of a steam nozzle E, the steam having a pressure of 75 lbs. per sq. in. enters the nozzle through a valve to which an arm E is attached, by means of which it can be adjusted so as to produce the desired velocity. In order to adjust and indicate the velocity an anemometer is used, and a scale constructed which indicates the velocity by means of a pointer attached to the arm. The gas is conducted to the apparatus by the pipe D into the gas tank, to which is attached a meter for measuring accurately the quantity of gas entering the holder. By weighting the gas tank, the gas will be forced down the pipe C into the wooden box, the inflow being regulated and adjusted by a nozzle having a pointer and scale F attached, to show the percentage of the gas mixture. 8AFBTT LAMPS. 433 The end of the pipe C, where it enters the box, terminates in a funnel-shaped opening which is covered with a gauze so as to prevent the flame, in case of an explosion caused by a lamp, from entering the gas pipe and conmiunicating with the gas-holder. This apparatus can only be used when a supply of coal gas is available. Trimming and Gleaning Lamps.— Probably nothing is more important as regards safety lamps than proper cleaning, trimming and fitting together of the various parts of which they are composed, for this part of the work bears directly upon the safety of the whole colliery. While the object to be aimed at is to get a good safe lamp, giving out a good light, simplicity of construction is also to be greatly desired, and this is wanting in many lamps brought before the public. When it is considered that at some collieries from 500 to 1000 safety lamps have to be cleaned, trimmed, and fitted together every shift, the necessity of simplicity in construction is at once apparent, because, if a lamp is complicated and consists of a great many parts, there is a great probability that, in preparing a large number for use, some may be imperfectly put together, and however safe a lamp may be when in perfect order, it may become most unsafe under these conditions. The principal parts of a safety lamp which are liable to get out of order, or may be improperly fitted together, are the gauzes, the glass chimney, and the joints between the latter and the metal. The glasses used for safety lamps should be of the best quality, ground smooth, and parallel at the edges ; glasses with chipped or rough edges should be discarded, for it is almost impossible to get tight joints where they come in contact with the metal rings. In the latter, ' washers ' of asbestos millboard should be introduced, which will give a good bearing surface to the edges of the glass. Washers of leather or india-rubber are not to be recommended, as they are perishable and shift their positions if they become strongly heated, which often occurs. The gauzes should also be carefully examined daily, and thoroughly cleaned so as to free them from any oil or coal dust which may have clogged the meshes while underground. At the majority of collieries the gauzes are cleaned by hand, and where the lamps are not very dirty this does well enough, if good brushes of the proper size and quality are used, but in collieries where the workings are muddy and the dirt adheres firmly to the gauze, the lamps are more difficult to clean, as the dirt adheres strongly to the gauze and cannot easily be removed. When this is the case, the lighting power of the lamp will become very inefficient, as the necessary air for proper combustion is unable to reach the flame. Machines either worked by hand or steam power are now used for cleaning the gauzes and glasses. By this means the gauzes are cleaned more thoroughly, and are not subjected to such rough treat- 28 434 PRACTICAL COAL-MINING. ment as when cleaned by hand, there being also an economy in labour, an experienced man being able to clean 300 to 400 gauzes per hour. Filling and Lighting Lamps, — ^As already stated, the utmost care should be exercised in charging safety lamps with oil, especially if the oil used is what is termed a * light ' oil, such as petroleum, naphtha or benzine, either of which is of a highly inflammable nature, especi- ally when the temperature reaches a certain point. These oils, as a rule, have a very low 'flash' point (about 70" F.), and when they reach this point they give off a dangerously combustible vapour which will readily explode if brought in contact with a light. At collieries where these oils are used, the lamp-room should be so arranged that the lamps can be filled in a separate apartment to that in which they are lighted before distribution to the men. It wiU also increase the security against fire or explosion if the filling tank containing the oil is situated in a special vault outside the lamp-room, and a pipe led from it to where the lamps are filled. Dripping pans should always be provided below each filling tap to receive any excess of oil. The dripping pans should be emptied at frequent intervals, as it is often from the overflowing or upsetting of one of these that accidents occur. Tanks which work automatically are sometimes used for filling the lamps. Such an apparatus consists of an iron tank which holds 10 to 15 gallons of oil, and by means of a three-way cock placed at the bottom of the tank, the small quantity of naphtha necessary for the filling of a lamp is drawn from the tank into the glass reservoir, and by the turning of the cock is entirely shut off from that in the tank. When the sponge in the lamp will absorb no more oil, the outflow from the reservoir stops automatically. By this arrangement safety and economy are secured. NoU. — For students who derire more detailed information as to safety lamps, the anthnr would recommend Tha Report of the Roycd Commission on Acddent* in Mines, 1886, where over one hundred such lamps are figured and described. OHAFTEE XV. SURFACE ARRANGEMENTS, COAL CLEANING, ETC. Siding Accommodation. — For the handling of a large daily output of coal, plenty of siding accommodation both for loaded and empty waggons should be provided. Many large collieries provide sidings for 200 or 300 loaded trucks, or for one day's output. This will be all the more necessary if the colliery is situated at a considerable distance from the main line, and a clearance is effected only once or twice daily. With the modem practice of separating the coal into many different classes for the market, the number of sidings requires to be greater than formerly, when it was customary to simply separate the dross from the round coal. From various causes the ground at •*\cSi Wonsff5p^ nSWtJlQuse 0* Phn shewing Surface Arrangement e^„j^ ri riilSB /^«i^^^^^•^*g^JM/l^ Offi Wi/tJiog £ngmes £iectrtePtmC Fig. 463. — Plan of Surface Arrangements. disposal may be limited in area for sidings, in which case it is im- possible to provide large storage lyes for loaded waggons. As to the general arrangement of surface buildings, such as engine-houses, boilers, screens, etc., the area and disposition of the ground inclosed will largely determine the matter for each individual colliery. A general plan of surface arrangements is shown in fig. 463, taken from those of a large colliery raising from 1200 to 1500 tons of coal daily. Inclination of Sidings, — The proper inclination for colliery sidings is an important matter. From the author's own experience he has 435 48S PFACTICAL COAL-MINING. found that the beet gradient behind the screens is about 1 in 70 for the empty waggons, with the inclination towards the shaft, while 1 itt 60 to 66 is best suited for the loaded waggons in front of the screens. With these gmdients the waggons should move freely in all weathers. BoUers. — The boilers used at collieries niaj be of either the ordi- nary egg-end, or of the Lnncashire or Comi^ types. Where rapid steaming and high pressures are required, the I^noashire boiler is the best to use, and also, as a rule, more economical, convenient, and durable. If large grate area is required, low pressures, and low first cost, the egg-end type of boiler may be found better suited. _D_L. FiQB. Uf, 46 S. —Longitudinal tmd Cross Sections of Comish Boiler. Comith Boilers. — Cornish boilers consist of a cylindrical shell a, with flat ends, and having near the bottom a smaller shell or tube 6 (figs. 464, 466), which passes through the larger one and forma the furnace. The products of combustion pass from the furnace to the end of the tube, and return by the two side tlucs // to the front of the boiler, pass into the bottom flue g, and so reach the chimney. By this arrangement the f;ascs are reduced in tempomture before com- ing into contact with the lioltom of the boiler, where all the sediment collects, find there is therefore no danger of burning the plates on the under aide of the boiler. SURFACE ARBANGKMENTS, COAL CLEANING ETC. 437 Laneaahire Boilers. — This type of boiler differs from the Comish in having two iatemal furDBCe tubes ioBtead of oue. The separate ftimaoes are intended to be fired alternately, so that while one ia giving off smoke and unbvimt gases, the other is burning hrisklj, and yielding its maximum heating effect. By this arrangement the mixture of smoke and unbumt gaaes from the 'green ' fire are con- sumed in the flues, where they are raised to the oeceBsary tempera- ture by the gases coming from the bright fire. The method of ventilation and draught ia similar in the Lancashire to that in the Comish boiler. The furnace gaaes pass to the end of the famace tube, and thence by the flue underneath the boiler to the front, where they divide and pass by the Elide fluee to the back of the boiler, from whence they escape into the chimney. Figs. 466, 467 show across and longitudinal section of the seating of •1 Lancashire boiler. The aide flues and closing tiles should be of the Flos. ISG. 4fl7. — Longituiliaal sad Crosa Sectioiis of Lancashire Boiler. best firebrick. Tn order to increase the heating surface and promote a better circulation of water, the furnace tubes of Lancashire and Comish boilers are often fitted with water tubes, those known as the 'Gialloway' tubes being the best known and the moat generally used. Such tubes have their disadvantages, however, as they tend to cool the furnace gases and retard combustion. The Comish boiler variee from 16 to 30 ft. in length by 6J to 8 ft. in diameter, the diameter of the furnace tube being 3} to 4^ ft. The length of a Laocashire boiler varies from 20 to 36 ft., and the diameter from 5} to 8 ft., a size much used for colliery work beiug 27 ft. 6 in. X 7 ft. 6 in. diameter. The furnace tubes are usually about 2 ft 6 in. or 2 ft. 9 in. diameter. Boileis of either type ought to be supplied with a safety valve, steam-gauge, glass water 438 PRACTICAL COAL-MINING. gauge, stop valve, water floaty sludge, steam and feed water pipes, blow-off cock and pipe, damper, eta Accidents t* Boilers. — Accidents to boilers are generally due to the following causes, viz., defective water supply, corrosion and incrusta- tion of shell, or defective safety valves. Accidents also happen from plates getting worn thin, or rivets becoming fi-actured. In the case of a defective water supply, if the water-level becomes dangerously low in the boiler the fire should on no account be with- drawn, as this procedure may accelerate an explosion by the sudden cooling of the plates ; the fire should be damped with small coal or ashes, the damper put down, and the boiler allowed to cool gradually before water is put in. Incrustation in steam boilers generally aiises from the presence of acids in the feed water, such as sulphate or carbonate of lime. If the impurity is found to consist almost entirely of carbonate of lime, the feed water may be treated by the addition of caustic lime or milk of lime, or by what is known as Clark's process. When carbonate and sulphate of lime are both known to be present^ the feed water may be treated with caustic soda or soda ash. With both of these methods, considerable expense is involved, as large tanks are required to hold six to eight hours' water supply; and instead of treating the feed water in any way, it is allowed to enter the boiler and the lime precipitated in the boiler itself, and the sediment blown oflf frequently. Boilers ought to be carefully inspected, internally and externally, and reported on every three months by a competent boiler inspector. Evaporative Power of Boilers, — Theoretically 1 lb. of coal should evaporate from 12 to 16 lbs. of water, at 212** F., the actual amount depending on the quality of the coal. In practice a Lanca- shire boiler will evaporate 8 to 10| lbs. of water at 212* F. per lb. of coal burned, and a Cornish boiler 7 to 9 lbs. of water per lb. of coal. The weight of water which can be evaporated per hour for any given size of engine may be found by the following formula : ^ _ D« X 7864 X L X 2xRx60xa ^ 1728 Where W equals the weight of water to be evaporated per honr ; D the diameter of cylinder in incDes ; L the lensth of stroke in inches; R the revolutions of crank per minute, and a the value of 1 cub. ft. of steam at given pressure. Bxample, — In an engine with a cylinder 20 in. diameter, a 24 in. stroke, and making eighty revolutions per minute, what amount of water would require to be evaporated per hour if the steam pressure is 66 lbs. per sq. in. I Here the value of a= '1638 lb. at 66 lbs. absolute pressure. • ^_20'x-7864x24x2x80x60x'1588_g^^g.g^^^^ 1728 ■" I • • SURFACE ABBANGEMENTS, COAL CLEANING, ETC. 439 Rate of OanUntstion. — ^The rate of ooinbuntion of fuel iu the furnaces of steam boilers is usually expressed in pounds of coal consumed per sq. ft. of grate surface per hour. In ordinary boilers the rate of combustion is from 15 to 20 lbs. of coal per sq . ft. of grate per hour. Strength of BinUrs. — The strength of boilers depends on their construction and upon the material of which they are made. Boilers are now generally made of best mild steel, with the exception of the manhole mouth-piece and longi- tudinal bolt-stays which are usually of wrought-iron. The tenacity of wrought-iron is giren at 50000 lbs. per sq. in., and that of steel for boiler plate 80000 to 90000 lbs. per sq. in., and a factor of safety of 6 to 8 is usually allowed. Let t represent the required thickness of plate in in. ; p the working pressure in lbs. per sq. in. ; d the diameter of boiler in in. ; and M the factor of safety. Then for wrought-iron boilers t=^— x M or p- "7 (single riveted). And t='^- X M (double riveted). 60000 ' For steel boilers t=^^ x M ofp=^^]^^^ (single riveted). 70000 dxM ** And tss P^ X M (double riveted). 90000 Examjde. — What thickness of double riveted boiler plate would be required for a steel boiler 7} ft. diameter to work at a pressure of 80 lbs. per sq. in. ? Here t^^^J^'^J^ x 8=?;^^ = '64 in. or about H of an in. 90000 75 &Mniple. — What would be the bursting pressure of a single riveted steel boiler 7 ft. diameter, with plates | of an in. thick t Herep=^^7Q000^tx70000^g^Q.3 j^ .^^ ^ rf 84 ^ ^ Low and Bevis give the following formula for the safe working pressure ! 8000 x 2t pss — ; where <= thickness in in., and (2= diameter of shell in in. a For the strength of boiler tubes, plain iron, Fairbaim gives the formula : P=3 — ^ — ; where P= collapsing pressure per sq. in.; L= length of tube li X LI in ft, and Ds diameter of tube in in. Where great accuracy is not required fi may be substituted for fi-^. Number of Boilers required, — The number of boilers required at a colliery will depend upon the class of boiler used, the kind of fuel supplied, and the number of engines to be simultaneously supplied with steam. A good Lancashire boiler, consuming about 7 cwts. of good coal per hour, should suffice for an engine of about 200 horse power, but at collieries where the fuel supplied for firing is often of a very inferior quality, about 180 horse power woidd be furnished per boiler, or even less. One spare boiler should be allowed for eveiy four or five in use. 440 PRACTICAL COAL-MINING. Au approximate method of estimating the boiler requirements is to allow one 28 ft. x 7 ft. Lancashire boiler for every 13000 cub. ft. of steam required per hour. Boiler Chimneys. — Chimneys or stacks may be either square, octagonal, or circular, the circular form being the best shape, but at the same time more expensive to build, as the bricks require to be specially made for each section of the chimney. Plenty of area should be allowed in chimneys, as it is useless to make large flues at the boilers and not to have a corresponding area in the chimney. The area at the top should be about the same as at the boiler flues. The following formula may be employed for chimneys, taking the consumption of fuel at 21 lbs. of coal per sq. ft. of fire grate per hour as a basis : — A = —j=- or ^H = — r— ; where A = area of chinmey in sq. ft. at top or smallest part ; G » area of fire grate in sq. ft. ; and H= height of chimney in ft. above fire bar leveL If the coal consumed is likely to be lower than 21 lbs. per sq. ft. •07 W of fire grate per hour, then the formula A = «— may be employed, W being the actual weight of fuel consumed in lbs. per hour. The height of a chimney will depend on the number of boilers and the total coal consumed, and is often determined by local considera- tions, especially if the colliery is situated near a town, as the authori- ties then often specify a certain minimum height for chinmeys. Chimneys, as a rule, should not be much less than 90 or 100 ft in height * The following table gives the height of chinmey according to the weight of coal consumed : Weight of Coal Height of Weight of Coal Height of consumed per hoar. Chimney. consumed per hour. Chimney. 100 lbs. and under 60 ft 8000 lbs. and under 160 ft 600 „ „ 100 „ 4000 „ ,, 180 ,, 1000 „ „ 120 „ 6000 ,, and upwards 200 ,, 2000 „ ., 140 „ The chimney should be built up on good solid foundations, rock, if possible, with a solid bed of concrete 2 to 3 ft. thick for a base, the brickwork being built up vertically for a certain distance and gradu- ally tapered off in 4^ in. courses to the required size. The thickness of brickwork for chimneys depends on their height, but except for very small chimneys it should never be less than 9 in. at the top. The outside batter should be from ^ to ^ in. per rising foot or about 1 in 56. Banking-Out. — Probably few things have undergone more changes in recent years than the banking-out arrangements at collieries. It • The Ptaetical Bnginrer's Pocket Book, 1897, p. 67. SUKFACB ARRANGEMENTS, COAL CLEANIKG, ETC. 441 was, and is still at a large number of oollieries, the general practice to cover the landing-stage with flat-sheets or iron plates on to which the tubs could be drawn when taken from the cage, and turned in any direction required. No doubt this system has its advantages, but it requires a great deal of hand labour that might otherwise be dispensed with. When new collieries are being laid out, flat-sheets are now often dispensed with altogether, and lines of rails laid up to the cage. Fig. 468 shows a banking arrangement on this principle, laid out for dealing with a large daily output. [ Travmlling Belt Travelling Belt [ Travmllinq Belt c^ I Trsvelhng Belt f ers Weight Fio. 468, — Banking Arrangement. The successful working of such arrangements has been greatly assisted by the introduction of tipplers and the creeping chain. As the lines of rails from the cage on the full side must have an inclina- tion towards the screens, to allow the tubs to run freely, there must be a corresponding inclination against the tubs on the empty lines of rails, which would involve labour to bring the tubs to the cage if 442 PRACTICAL COAL-MINING. done by hand. To avoid this, the creeper chain is used. The creeper consists of an endless chain made on much the same prin- ciple as a travelling belt. At set distances apart are fixed upright pieces or ' fingers ' for catching the tubs and carrying them forward to the desired position. The chain works round octagonal wheels at each end, and is supported throughout its length by rollers fixed in standards. On the side of the pit-head where the full tubs are taken off, the rails, as already stated, are laid at an incline in favour of the tub. The tubs are first taken over the weighing-machine, and then by their own weight run into the revolving tipplers, from which, when empty, they pass to the creeper and are hauled up to the level of the cages again. Instead of a 'creeper' a steam or hydraulic hoist is sometimes used to raise the empty tubs to the desired leveL The disadvantage of such an apparatus is that it is not self-acting, and is therefore more costly in working. The hoists themselves are also expensive to erect^ especially if the height is great, and the raising piston must of necessity be long in proportion. Tipplers. — The simplest and most common kind of tippler for emptying the contents of the tubs on to the screens used to be an arrangement of two rails bent up in the end, and pivoted on an axle placed beyond the centre of gravity from one end, so that) when the tub was run to it, it was tipped up and emptied, and had then to be drawn back into its original position. This tippler is now seldom adopted, as the coal had to fall too great a distance down to the screen, and also necessitated the tubs being provided with a door at one end for emptying, which is a disadvantage for under- groimd work, as such doors are apt to fly open and allow the ooal to fall on the road. Rotary Tipplers, — During recent years a large number of tipplers have been designed, chiefly on the rotary principle, in which the tub is turned through either a half or full circle. One of this class is Wood k Burnett's, which is shown in figs. 469, 470. It is driven by a chain and sprocket wheel arrangement^ or by toothed gearing, the starting and stopping gear being the same in either case.* The tippler consists of circular cast-iron wheels A, riveted together by bars and angles in the usual way, and supported on four cast-iron rollers B. A counter shaft C, driven by the screen engine, carries the sprocket wheel D, attached to a friction clutch E, by means of which the tippler may be thrown into gear with the shaft C. The friction clutch also acts as a brake-wheel, a wrought-iron strap passing round it for that purpose. The sleeve of the friction clutch and the brake-lever are moved by means of a weighted bell-crank F, so arranged that when the end a is de- pressed the brake is applied and the friction clutch thrown out of gear. On releasing it the weight causes the brake to be released, and the friction clutch gears on again. The tippler is started by means of * Trans. I. M, E,, vol. ix. p. 282. BUByACK AEBANQEMENTS, COAL CLEANING, ETC. 443 tKe hand-lever M, so that the wedge L is withdrHwn from the bolt I£.j the l&tter is thus ahorteuod, allowing the weight on the lever F Fioa. 469, 470.— Wood and Burnett's Rot&rj Tipplar. to 6l11, by which the brake is releaaod and the friction olutoh put into gear. At the eame time the lever 0 faJla clear of the atop I, and the tippler at onoe commences to rotate. 444 PRACTICAL COAL-MINING. The hand-lever M is then allowed to fall back and to piish the wedge L through the aperture in the box, thus lifting the end of the lever G into position readj to engage with the stop I, when the revolution of the tippler has been nearly completed. The lever G is pushed down by the stop I, and so applies the brake and throws the friction clutch out of gear automatically and simultaneously. An auxiliary attachment, consisting of a treadle, lever, and rods c d and e, is applied, so that the tippler can be stopped during any portion of its revolution, if necessary. Heenan and Frotide'a Rotary Tippler, — This tippler is also of the rotary type, having the cylindrical frame supports! upon two pairs of rollers. The cast-iron ends As (figs. 471, 472) of the tippler are dissimilar, A having two grooves on the edge, so as to engage the friction wheel B when in motion. This friction wheel is mounted on an arm C, which is pivoted on to the countershaft D, from which the motion is transmitted to the friction wheel by the spur wheels £ and F, The countershaft D is driven from the screen engine, and is in constant motion. The arm C also carries a hand-lever L, by which the friction wheel is placed in contact with the grooved rim A of the tippler frame. An arm G, with a counterweight attached, is used to throw the friction wheel B out of gear, and to automatically stop the tippler at each end of the revolution. The lever H, having a small roller r and a pawl p mounted on one end, is pivoted loose on the shaft D, and its movement is transmitted by means of the adjusting screws s and a' to the arm C, and thence to the hand-lever L and friction wheels. After placing a tub on the tippler, the banksman pushes over the lever L, so that the roller r and the pawl p are lifted from the recess c on the rim A, and the friction wheel B is put into gear at one movement. On completing a revolution, the roller r drops into the recess c, throwing the friction wheel B out of contact with the rim A, and the pawl p brings the tippler to rest in the proper position for receiving another tub. Trayelling Belts. — After the coal has been passed over the screens to get rid of the small coal or dross, it is received on a travelling belt, where it may undergo a final hand-picking before being loaded into waggons. The belts are made of varying materials, according to the work to be done. For coal picking and conveying they are usually of iron or steel plates, link or woven wire, or of flat hemp or cotton belting with a hardened indiarubber face. Where only two kinds of coal have to be separated from each other, such as a cannel and a free coal, belting made of canvas faced with leather can be used with much advantage. The ordinary type of belt is made of steel plates 9 to 1 2 in. broad, |^ in. to ^ in. thick, fixed to iron or steel link chains that fit into a split polygonal drum at each end. The belt is sup- ported usually on cast-iron rollers keyed to a shaft, which runs in pedestals fixed to the supporting beams. The delivery end is provided SUBFACK ilBBAKGSMSKTS, COAL CLEANIKG, ETC. 445 "tA/v/' 446 PRACTICAL COAL-MINING. with tightening screws and slotted seats to take up any slack on the chain (see fig. 473). In driving, the usual type of hexagonal wheel is employed, two being placed at each end of the belt. These belts have usually a very slow motion, travelling at the rate of 40 to 80 ft. per minute. The length of the belt may be anything between 30 and 150 fb., but where they are used for picking the dirt out of the coal 30 to 40 ft. ? L ^ ft Fio. 478— Tightening Screws for Belt is a usual length. Their width varies from 2 to 4 1 ft., 3 ft. or 3 J ft. being a good width where the picking is done from one side only. These belts are now often of steel wire rods woven across each other, as shown in fig. 474, but this type of belt can only be used for large sizes of coal. Elevators. — When the small coal or dross is dropped through the screens it generally falls into a large hopper or dross pit, and is thence raised by means of elevators to be further treated either by dry or wet cleaning. These elevators are made on the same principle as tlie travelling belt. Two long endless chains with long single links fixed alternately inside and outside each other, having an iron bucket fixed to them, pass round a hexa- gonal wheel at each end. The length of these elevators and their speed depend greatly upon the quantity of coal to be handled, and the height to which it requires to be raised. An average speed is 300 to 400 ft. per minute. Arrangement of Cleaning Apparatus. — We have described the various parts of a coal-cleaning arrangement^ either of which is seldom used by itself, but all of them being used in combination, whether the coal is subjected to a dry or wet cleaning process or not. If the coal can be cleaned sufiiciently well without washing, the arrangements are greatly simplified, and less outlay in plant is Fio. 474.~SfgroeDt of Wire Belt SURFACE ARBANGKMENTS, COAL CLEANING, ETC 447 required. Fig. 475 illustrates an arrangement of an ordinary cleaning plant. It must be remembered, however, that a given arrangement of plant will hardly ever suit two different collieries, as the screening arrangement will altogether depend on the quality of the coal, the amount of dirt in the coal, and the kind of coal in demand. Goal Gleaning. — Under this heading may be included the various methods of washing and sorting the coal when brought to the surface. The processes employed may be divided into two groups : — Cleaning by mechanical means ; Gleaning by taking advantage of the physical properties of the mineral. Under the first head may be included (a) screening ; (b) washing the mineral to cleanse it from mud, clay, shale, etc.; (c) hand-picking; and (d) sorting. Pithesd LevBi Travelling Belt Tripina or Coat • _ Swinging Platform Conveyor I Coal I CJro**] p^ Fig. 476.— Cleaning Plant. Screening the Goal. — This is usually the first operation to whick the coal is subjected after it arrives at the surface. The screens employed may be divided into classes, viz.. Fixed inclined screens, with movable bars. Revolving screens. Jigging or shaking screens. Fixed Inclined Screens are very largely used, but they are fast being superseded by the shaking type of screen. When the former only are in use, the coal is picked by hand, and, as a rule, this is the only cleaning it undergoes. Fixed inclined screens are usually made of iron or steel bars set at an angle of about 30* from the horizontal, so that the coal can just move slowly forward. The bars may be made of different shapes, but are very often rectangular in section, about 1 in. thick, 3 to 4 in. deep, and 10 to 15 ft. long, according to the quality of coal dealt with. A soft coal generally requires a longer screen than a harder quality, as there is more dross to be got rid off*. The openings between the bars vary from ^ in. to 1 ^ in., (48 PRACTICAL COAL-MININQ. ftocording k> requirements, and aometimes by agreement with the landlord of the coalfield, as different ' lordships ' or royalties are often payable on different qualities or sizes of coal. Revolning Screens. — These scrcenB are made like a large revolving riddle fixed on a central aiia. They are largely used for dry-cleaning and sorting the smaller qualities of coal after they have been passed over a fixed or jigging screen. They may be made either of wire netting or sheet-iron p&tcs with circular perforations to suit the siie of coal required. A revolving screen is usually made to sort or separate two or three different sizes of coal, different parts of the screen being provided with differently sized apertures, as shown in fig. 476. Jinking or Shakiiig Screens. — This class of screen is now almost exclusively largely used in place of the fixed bar typo for the screen- ing and sizing of coal. The screens are set at very slight inclination, 10° to 12* from the horizontal, and hence the coal descends very Fio. 476.— Revolving Screan. slowly, gets very little broken during the process, and can be thoroughly picked and cleaned. The screens usually derive their motion from arms attached to tlie sides, and which work eccentrically, giving the screens a rapid to-and-fro motion, the coal at the same time moving slowly forward. They are usually suspended to beams by means of tour rods fitted with adjustable screws for altering their inclination if required. Tho eccentric for driving has a short stroke, 3 to 6 in,, and makes about 60 to 100 revolutions per minute. The screens may be conatriicted of wire netting fixed in a frame, or of sheets of iron or steel with circular openings. The latter are very largely employed, and are preferable to those constructed of wire netting, as they last much longer and size the coal much better. Figs. 477, 478 illustrate the constniction of a jigging screen and the method of fixing it Coal Washing or Wet Cleaning.— Coal bolow a certain size, when mixed with foreign substance, is ditticult to clean properly without SURFACE ABBAMQBMSHTS, COAL CLEANING, SIU 449 A 949IJ qtUTIff |«» E ~dir^^^ •»imu tfuna ifc it 2| ^1 2C mtaij qiung i 1 CO s I 29 460 PRACTICAL COAL-MTNma. washing. Some coals are so intermixed with impurities that no other method than wet cleaning would he of any use. As small coal usually contains the highest percentage of impurities, it is usually dealt with in this way. The cleaning of coal may be performed in many ways, all of which are, however, based on the same principle, i.e. the differ- ences in density existing between the impurities and the coal. The different methods of washing coal are^ : (1) by an ordinary inclined trough washer with fixed stops ; (2) by a fixed trough washer with movable scrapers, of which Elliot's patent is an example ; (3) by mov- able troughs, such as the Murton and the Wood and Burnett washers ; (4) by continuous ascending current washers, such as the Robinson washer; (5) by intermittent ascending current washers, as in the Liihrig and Copp^ washers ; (6) by compressed air, as in the Baum washer. Choice of Washer. — In choosing a washing plant the most imporfr ant consideration is the financial one, and this is generally where the difficulty lies, for a certain class of machine may be expensive in first cost and yet may soon recoup the outlay by economy in working and in producing a cleaner and better quality of coal, while a machine that may be erected at half the cost may prove much more expen- sive in other respects in the end. An important point also is that the coal must be adapted to meet the buyers' requirements, while different kinds of impurities require different methods of treatment. M. Gallon states the position clearly when he says : — *' In the case of coal cleaning we are dealing with enormous quantities of a substance of comparatively little value, the profit on which is reduced to a minimum by competition. We are consequently forced to employ special machines as simple as possible in construction, and capable of treating considerable quantities. We must abandon all idea of treating coal by frequent repetitions of the same process, or, at all events, do so sparingly, so as not to burden the undertaking with heavy costs, and the operations must be carried on with simplicity and economy." For small quantities of coal, and where not much sorting is required, the trough washer is often foimd satisfactory, or, if a more thorough cleaning is desired, the ordinary ' Bash ' washer is as good as any for economical working. When large quantities have to be dealt with, and the coal requires sorting into a variety of sizes, some of the more expensive machines, such as the Liihrig or Coppde, may be adopted. Before any class of machine is fixed upon, the coal and its accompanying impurities should be submitted to a thorough analysis, the result of such a test often affording sufficient information for a decision to be arrived at. The three important points in coal cleaning are : — To remove impurities as far as possil)le ; not to allow any coal to pass away • The Practical EiujineerB Pocket Book, 1897, p. 828. SUPFACE ABRANQEMENTS, COAL CLEANING, ETC. 451 with the impurities; and to achieve these objects in the cheapest manner with efficiency. Trough Washer, — This is one of the earliest and simplest types of coal washers. It consists of a long, narrow trough divided into a number of stages by means of projecting pieces fixed to the bottom or sides of the trough. The trough is set at an inclination of 2 in. or 3 in. per yard, and a stream of water is allowed to flow continuously and sufficiently fast to carry the coal forward over the projections, while the heavier impurities fall to the bottom and are caught in the divisions of the trough. When a certain quantity of coal has been cleaned the flow of water is stopped and the refuse cleaned out, ready for another operation. An improvement on this form of trough, with stationary dams, is a travelling scraper on the endless-chain principle, which by moving along the bottom of the trough against the stream of water and coal, delivers the impurities automatically at the upper end of the trough. The dimensions of these troughs are from 50 to 80 ft. long, 2 to 3 ft. wide, and 10 to 12 in. deep. The trough washer is best suited for small quantities of coal ; it requires a large flow of water and entails extra labour, but it has the recommendation of being simple in construction and cheap at first cost. A trough washer 60 ft. long and 2 ft. broad, with revolving riddle and connections, can be erected for about £180. Elliot Trough Washer, — This is an improvement on the old trough washer. It consists of a wrought-iron or steel trough, about 18 in. wide at the bottom and 30 in. wide at the top, and having sloping sides. At each end a sprocket wheel is fixed, round which an endless chain passes, and attached to the chain at intervals of 6 ft. are fixed scrapers to fit the inside of the trough. The scrapers form stops or dams, which are slowly moved by the chain along the trough in the opposite direction to the flow of the water. The trough is set at an inclination of about 1 in 12, and the coal is admitted at the centre of its length and the water at its upper end. As the water runs down it carries with it the coal, which is lighter than the dirt, while the latter settles in the scrapers and is carried against the stream of water and delivered at the opposite end. Murton Coal Washer, — This machine, like the Elliot washer, is an im- proved trough washer. It consists (fig. 479) of an endless articulated steel trough belt, which is watertight. This trough revolves slowly round suitable drums at each end, the action being continuous and automatic. The clean-washed coal falls into a hopper at the lower end, the dirt or refuse is delivered into a dirt hopper at the upper end. The trough is constructed of steel, 60 ft. long, 3 ft. wide, 8 in. deep, and fixed at an inclination of 1 in 18. The supporting drums and rollers are mounted on a suitable frame. Inside the trough, at intervals of 3 ft., are dams or stops about 2 in. high. Method of Working. — The trough is set in motion and travels up PRACnOAL COAL-MINING. *t liZ 8URFACB ARRANGBMBNTS, COAL GLEANING, I£TC. 453 the incline, nnd towards the coal and water supply, at a speed of from 8 to 10 ft. per minute. The coal from the hopper H (fig. 479) and water from the nozzle £ are turned on in suitable proportions. The latter, carrying the coal with it, flows in a direction contrary to that of the trough to the coal delivery end D, where it is delivered free from impurities. The dirt falls to the bottom of the trough, and is arrested by the stops c c, and carried forward by the motion of the trough beyond the point £, after passing which it is agitated in such a manner that any coal mixed with it is liberated, and carried* back by a strong current of water from the supply pipe J to F, where it joins the regular coal feed, and is carried along with the rest of the clean coal forward to D. The refuse continues to be carried upwards to the end of the trough M, and as the belt moves over the drum A it falls off into the hopper. The trough is washed clean by the water spray «, and passes to the drum A' at the lower end D. The coal, when delivered at the lower end, falls into a spout^ with a draining plate (with 125 perforntinos -^ in. diameter per sq. in.), and the water is quickly drained away. About 450 gallons of water per minute are required when washing 400 tons of coal per day, but the same water can be used over and over again. Robinson WasJier, — This machine, which is shown in tig. 480, con- sisits of a truncated inverted cone, made of steel plates about 8 ft. diameter at top and 2 ft. diameter at bottom and 6| ft. deep. A strong shaft is fixed vertically, to run in the centre of the cone ; on this shaft is a strong cast-iron cross-head, to which are bolted four cross arms. To each of these cross arms are bolted three hravy wrought-iron bars, but outwards at the bottom, and projecting down so as almost to touch the sides of the cone or washer, and on the bottom of the driving shafts are also bolted four shorter arms, as shown in illustration. In practice the coal passes into the washer from the spout A into the centre ring B, while the water supply is forced in at tiie bottom at E and through the perforations G. The coal is kept in a continual state of agitation, and as it sinks into the washer it is met by the upward current of the water ; and, being lighter in weight than the impurities with which it is associated, is floated upwards, as indicated by the arrows, and overflows at D. T\\Q impurities sink downwards and are collected in the chamber J. When this chamber is filled, the upper valve H is closed, and the lower valve H' opened ; this allows the accumulated refuse to be discharged, after which the lower valve is closed and the operation repeated. The shaft, with cross-head and depending arms, revolves at the rate of 14 or 15 revolutions ])er minute. In fig. 481 is shown a general arrangement of a Robinson washing plant The clean coal passes from the washer on to inclined perforated screens or shoots, and is here freed from the water, after which it is cither carried by means of conveying machinery to storage bins, or 454 FBACTICAL COAL-HININO. fiills direct into the vaggona. The water from the overflow b coUeuted in aottling ponds, and b; meana of a pulsometer pump is again forced into the washer for further ui>e. The Kobineon washer is cheap to constmot and maintain, and requires little water, but it largely depends for its efficiency on the uttention and skill nf the man in charge, who may oft«n be tempted to pass more coal through it than it can efieotunlly deal with. Theee Fio. ISO.— Ililiiiiiaii Washor. machines can be made to wash from 20 to 40 tons per hour. The coat of a Robinson washing plant to treat 20 tons per hour is from £250 to £350. Liihrig and Copp^ Machines. —A paper read beforo the South Wales Institute of Mining Engineers * gives an elaborate description of the construction and working of these machines. The following abridgment t will, however, suffice to eiplain their action. The machines are made in two sizes, the larger dealing with coal from 6 in. to J in. in thickness, and the smaller taking fine coal and powder. SUBFACB ARBANOBMSNTS, COAL CLBANTNO, ETC. 455 "The larger, or nuts machiue (Hgs. 482, 483), is of the ordinary con- tinuous jig type, and consists of two compartments A and B, in one of which the piston works, while the other is provided with a perforated strainer, slightly inclined from front to back. The piston P receives an up-and-down motion by being connected to cranks on a horizontal shaft, and the amount of this throw can be varied from If to 4 in. An opening W runs along the front of the washing compartment^ and through this clean coal continuously passes away. The shale is dis- charged through a small cylindrical compartment D, connected to the ftwvrdiAN Fio. 481. — General anraDgenieut of a Robinson WasLiug PLmt. side of the casing, but which starts above the level of the strainer, leaving a free space between the strainer and the lowest end of the compartment of about 3 in. It is open at both ends, and commimicates with the outside of the machine through the opening R. It is pro- vided with a sliding door which regulates the discharge of the shale. " When the unwashed coal is introduced into the machine, and the piston descends, it drives water into the compartment B^ and lifts the bed of the material resting on the strainer. On the return stroke, the heavier dirt falls faster than the lighter coal, while in the upstroke 456 FBACTICAL COAL-UIMINO. the lighter coal is lifted farther than the heavier dirt ; the result is, that tho two Bubstanoee separate into layers, the coal being, of courae, the higher. PiOB. 482, 183.— Uhrig and Oappiu Mucliltiw. " The Ftltpar Waslier is of similar conatructioii, but differe materi- ally in its method of working. It consiste of a box, divided into two oompartmente by a longitudinal partition, in one of whiob the mstoa works as before (figs. 464, 486). It is also generally dividea into SURFACE ilRBANGEMENTP, COAL CLEANING. ETC. 457 two or Bometiiues three compartments in the direction of its length, each communicating with the other by openings o along the side, and through these the wtished coal pajsses away. In tlie nuts washer the holes through the sieve are smaller than the size of the material being treated, and consequently no discharge takes place through them. In the felspar machme they are larger than the material, and the dirt passes through the sieve into the lower part of the apparatus Three sieves are generally employed. The dirty coal is introduced at one ODd and graduaUj pLes down over the remaining giutings, the clean material being finally discharged at the opposite end. "The chief peculiarity is the introduction of a layer of felspar, from 2 or 3 in. thick, on each sieve, whose specific gravity is greater than that of the material to be concentrated, and yet less than that of the gangue. The sizes of the particles of this bed are larger than the holes in the sieve. The whole framework of the machine is Figs. 484, 485. — Felspar Machines. tilled with water up to the level of each sieve, and as the pistons work up and down, a volume of water is forced through the holes in the bottom of each sieve, lifting the bed and the layer of material on it, and then allowing the whole to fall again on the return stroke. The lighter coal rises to the surface, and the heavier dirt gradually finds its way through the bed of felspar, when it falls into the bottom of the compartment to be removed from time to time. It is essential for thorough cleaning that the size of the felspar should be as small as allowable, and that the particles of mineral forming the bed should be of convenient density, have well-defined rectilinear angles, and be of great durability to resist wear and tear. A point of con- siderable importance is the proper regulation of the delivery of water, which is controlled by a tap ; upon this depends the progress of the material and the time it is operated upon. " For very dirty coal, perhaps no machine does its work so efficiently as this ; indeed, everyone gives it the character of removing dirt. It is, however, expensive in the first cost, but requires little attention. Much depends upon the percentage of dirt originally present in the coal If it is small, and, say, one- half of it is removed, the coke from 458 PRACTICAL COAL-MINING. the resulting product is a fair one ; on the other hand, where the dirt amoimts to from 15 to 30 per cent, and only 3 to 10 per cent, is taken away, the coke is very had. With a duty coal, probably it is best to use machines of this type." Baum Washer. — This machine applies a new principle to coal Fio. 486.— Baum Washer. washing, inasmuch as compressed air is used, instead of a vertically reciprocating piston, for producing the oscillations of the water through the bed of the jigger. Ey this method it is claimed that all noise, vibration, and shock are done away with, and that less power is required than in an ordinary piston machine. Fig. 486 shows a 8URFAGB ARBAN0BMENT8, COAL GLEANING, BTG. 459 cross section of one of the jigging machines.^ The jiggers are con- structed of steel or wrouglit-iron plates connected by angle irons. The water-box m is closed at the top by a horizontal plate, to which is fittfd a piston valve casing g, in which works a piston or cylindrical valve Jif actuated by the eccentric n, and having ports or openings in the sides to control the adnussion and exhaustion of compressed air to and from the upper dosed-in part of the water-box m. Openings j are provided in the sides of the casing g for the escape of the com- pressed air from the water-box ; and o is a stop valve for admitting or shutting off the compressed air. The latter, at a pressure of 1 1 to 2 lb& per sq. in., is drawn from the receiver, to which it is supplied by the air compressor. In the coarse jigging machines the valye h makes from 50 to 70 strokes per minute, and in the fine jiggers from 75 to 110 strokes per minute, the alteration in speed being effected by means of coned pulleys on the driving and countershafts. The jigger sieve 0 is of f in. mesh for the coarse and ^ in. mesh for the fine jiggers. At the top of the machine there is an overflow bar d, over which the coal from the coarser jiggers is carried along channels to special nut pockets; ff are two slides, adjustable by means of the levers tt\ for regulating the outflow of the dirt, which falls to the bottom of the jigging-box, and is conveyed away by means of a spiral conveyer u extending the whole length of the jig battery. It will be noticed that the mesh used in the fine jigging machines is larger than much of the material treated, and it might be supposed that some of the latter, including the coal, would fall through the sieve. The machines, however, can be so regiilated that the larger pieces of stone or shale are retained a considerable time on the sieve, and owing to the weight of material above them they set themselves parallel to the sieve and form a bed similar to the felspar bed em- ployed in the Coppee fine jigging machines. Cost of Coal Washing. — This will vary very much with the class of machine used, the quality of the coal, and the percentage of dirt accompanying it ; and also on the amount of dressing or pre[)aration the coal requires for the market. The following table t shows the cost per ton of washing by various machines in the year 1 886 : — Name of Colliery. Dry Cleaning. Wet Cleaning. TVpeof washer. previous to Washing. Barrow, lid. 2id. Robinson. Crushed. Aldwark Main, • ... 2fd. Trough. ti Nunnery, 8d. l-40d. »i Not crushed. Annesly, . 2id. to 3d. • • ■ *•• • • • Clifton, . . 8d. to 4d. 6(1. to 7d. Copp^ Ltthrig. Not crushed. North Motherwell, « ••• 07ii. II * TfWM, I.M.B,, vol. vii. p. 158. t Trans, M, /. Scot., Coal Cleaning Committee's Report, p. 179. CHAPTER XVI. SURVEYING, LEVELLING, AND PLANS. *'SuiiVEYiNQ is the art of ascertaining by measurement the shape and size of any portion of the earth's surface, and representing the same on a reduced scale, in a conventional manner, so as to bring the whole under the eye at once." *Surveying has also been defined by Mr Bennett H. Brough as " the art of making such measurements as are necessary to determine the relative positions of any points on the earth's surface. From such measurements a plan of any portion of the earth's surface may be drawn, and its area calculated." In ordinary mine surveying three objects are in view, viz., to obtain a correct plan and section of the underground workings ; to ascertain the correct position of all surface buildings, shafts, and otlier features, and the correct boundary line of the field or royalty to be worked, and to connect as accurately as possible the workings on the underground plan with the surface survey. t " All surveys are conducted on nearly the same principles, the difference consisting in the style of the instruments used in the work, and the different methods of calculating the various data coimccted with the survey." The instrument which is in most common use for ordinary under- ground surveys of mines is the miner's compass or dial, sometimes called the circumferentor. This is an instrument the chief use of which is to measure horizontal angles. As used with the loose needle the angles are measured in relation to the magnetic meridian, and as used with the vernier or fast needle the angles are measured either in relation to the magnetic meridian or in relation to any given base line. Tlie instrument consists essentially of two parts, a needle swinging freely on a pivot, and the dial on which the angles are read. When surveying with the magnetic compass it is most important to remember that the needle does not point to the true narth, and that the direction in which it points is subject to several variations from • A Treatise on Aline Stfrvevuig, by Bennett H. Brougli, p. 1. f Ibid. 460 8TJBVKYTN0, LEVELLING, AND PLANS. 461 time to time. It is more than 300 years ago since observations were first made on the variations of the needle, and we are therefore not without some data to guide us. In Queen Elizabeth's time, i.e, about 1580, the variation was about IT IT east; in Charles II.'s time, 1657, this variation had disappeared altogether and the needle coincided with true north. The needle swings backwards and forwards on each side of the true north like the pendulum of a dock, but with this difference, that it swings in centuries and not in seconds. Its maximum variation is 24** 48' on either side, and this is termed the secular variation. Taking the average between 1580 and 1880, the variation was 8^ minutes per year, and for the ten years between 1877 and 1887 tne total variation was V 12', giving an average of 7*2' per year. Since 1660, in which year there was no variation, the declination has been towards the west, attaining its maximum in 1820, and then gradually decreasing, so that at the present time the magnetic meridian is again approaching the true meridian. The average annual variation of the needle may be taken at 8 minutes. The magnetic needle at Greenwich at this date (1899) points about 16*" 30' to the west, as shown in fig. 487. At Edinburgh the magnetic declination is 3* greater than at Greenwich, while in Glasgow and Dublin it is 3" 50' greater. In the North of England the variation is about If degrees greater than at Greenwich. A very elaborate magnetic survey was carried out between the years 1884 and 1891, by Professors Riicker and Thorpe, to determine the amount of variation and the lines of attraction in the United Kingdom. Obser- Fio. 487. vations were made at 882 different places, and from their calculations and a map it will be possible to gain some idea how far local disturbances are likely to affect the needle at any given place. As regards such disturbances it is found that the north-seeking pole of the compass is attracted to certain regions and to lines which can be traced for scores or even hundreds of miles. These lines they (Riicker and Thorpe) call magnetic ridge lines* The principal ridge lines determined were as follows : (1) In the Scotch coalfield a ridge line runs from the neighbour- hood of North Berwick to the Clyde between Glasgow and Hamilton, turns south to Newmilns in Ayrshire, and finally runs in a northerly direction towards Ardrossan and Arran. (2) The Yorkshire coalfield is dominated by a ridge line which runs south-west from Harrogate towards Keighley, and follows the outcrop of the Millstone Grit to Matlock. • Trans, Inst. Min, Engs,, vol. ix. pp. 418-419. 462 PRACnOAL GOAL-MIKINa. (3) In the southern piirt of the Derbyshire coalfield the north- seeking pole of the magnet is attracted from all sides to a centre which is a little to the north-east of Nottingham. (4) In the Lancashire coalfield a ridge line runs from Kochdale to Wigan and Southport. (5) In the South Wales coalfield a ridge line runs from Risca to the south end of Ebbw Vale, and another passes from Brecon to Neath, and thence nearly due west through the centre of the coal measures. If these ridge lines are therefore drawn upon a map, and the varia- tion determined for places in their vicinity, the magnetic variation for any given locality may be pretty accurately ascertained. The amount of variation may also be approximately determined for any locality in Great Britain by drawing lines on a map in the following directions : * (a) From Winchelsea (Sussex) by point of Sheppey Island and Ipswich, the magnetic declination is 30 minutes lees than at Qreenwich. (b) From Gowes (Isle of Wight) by Basingstoke and Great Grimsby 30 minutes more than at Greenwich. (c) From Start Point by Teignmouth, Newport (Mon.), the Peak to Seaham r'30' more. (d) From the Land's End by Great Ormes Head, Skiddaw, etc., 2' 30' more. (e) From Peel (Isle of Man) by Wigton to Falkirk, 3'-20' more. If these differences are applied to the declination at Greenwich, the amoimt of declination or variation on each line may be obtained. For any place situated on one of these lines the value of the variation will thus be at once ascertained, and for a place situated between any two lines a proportional variation may be made from Uie values found for the adjacent lines. The variation of the magnetic meridian shows the necessity of recording on all colliery plans the date and amount of declination for the guidance of future working. Many accidents can be traced to the neglect of doing this at the time of drawing up the plan. The date of an old plan may be approximately ascertained by look- ing at the meridian line on it; thus, if a plan is found having a meridian with a declination of 2 T 00' west of the true north, we would say that it was probably made about the year 1864, the variation for that year having been 21* 03' at Greenwich. The needle is also subject to diurnal fluctuations. DiumcU Vanation. — In the afternoon the needle is drawn a few minutes to the west and in the early morning a few minutes to the • CcUiery Manager's Pocket Book, 1898, p. 161. SURVSTING, LEVELLING, AND PLANS. 463 east. The needle stands at its mean position a little after 10 a.ni. and a little before 7 p.m. The variation is greater in summer-time than in winter, but seldom exceeds about 10 minutes. This varia- tion must be taken into account when making surveys in which accuracy is required, but under ordinary circumstances, such as the quarterly extension of colliery plans, the variation is too small to cause any appreciable error. The declination of the needle may- be due to various causes, such as : — (1) The presence of masses of magnetic rock. (2) Induction currents. (3) Magnetic storms. The chief mineral that attracts the needle is magnetite, which is foimd in masses, veins, and sands. Tops of mountains in the Northern Hemisphere attract the north-seeking end of the needle. Beaches are often covered with magnetic sand; for instance, in Rothesay Bay there is a large bed of this description. Other minerals that attract the needle are magnetic pyrites and native iron. All crystalline rocks contain minerals which deflect the magnet more or less, and rocks which are dark-coloured do so more than others, as such rocks usually contain a fair proportion of iron com- pounds. Sometimes the needle is affected in positions where no such rocks are visible, a notable instance of this being at Melton-Mowbray, where there are no igneous rocks in the immediate neighbourhood, although the needle is deflected through as much as 67*, which may be due to the presence of large masses of basaltic rock lying beneath the surface. Prof. A. W. Rticker,* speaking of this source of attraction, says: — ''Magnetic rocks are often permanently magnetized, and may deflect a compass held close to them through 40* or 50*. The permanent magnetization is, however, irregular, and at a compara- tively short distance the disturbing effect appears to be due almost exclusively to the uniform magnetization produced by the earth's magnetic field." The general conclusions which he comes to, both as regards theory and experiment, are: — (a) "That dykes and thin uniform basaltic sheets produce no measurable effects except at distances from their edges, which are small midtiples of their thickness ; (b) That isolated masses of trap-rock, a few square miles in area, produce no important magnetic effects at distances comparable with their linear dimen- sions." Induction Currents, — Induction currents may be produced by the neighbourhood of currents or of magnetic bodies inducing them, i,e, rocks containing iron or its compounds. * Trans. Inst, Min, Sng. , vol. ix. p. 420. 464 PRACTICAL COAL-MININQ. Magnetic Storms, — The irregular fluctuations of the needle which occur from time to time proceed from magnetic storms. The word storm in this connection does not necessarily imply violent action, although occasionally the needle oscillates backwards and forwards. As a general rule, however, the needle becomes temporarily deflected some degrees beyond the normal variation over a large area, some- times for 24 or 48 hours. Magnetic storms are invariably connected with displays of aurora, and, in some unexplained manner, with the occurrence of spots on the sun, and, as shown by Prot Balfour Stewart, they commonly occur at intervals of ten or eleven years^ when the sun spots are at their maxima. If the compass is used during one of these storms the needle sometimes becomes practically worthless for the time being. Influence of Rails on the Needle. — The presence of iron or steel may cause the needle to deflect. Cast-iron in small quantities does not seem to have much influence, and those used underground at many Scotch collieries (weighing 28 lbs. per yd.) have so little effect that the surveys of those mines are almost invariably made with a free needle. Malleable iron rails have a more appreciable eflect. With rails weighing 12 to 15 lbs. per yd., the deflection is seldom greater than 2" when the compass is placed in the centre of the two rails, and about 3 ft. above the ground. Steel rails of the same weight exert more influence, and the needle is often deflected over as much as 10** to 15** in the presence of such rails, so that special precautions become necessaiy in making obser- vations. Steel ropes and tools will also afiect the needle, and in order to get a true reading the compass should be planted at least 15 ft. from any metal, while the presence of a large mass of metal necessitates its being placed still further away. In highly inclined workings, with the dip towards the north, it frequently happens that if a road is driven in the direction of the magnetic meridian, the rails become strongly magnetized on account of the earth currents passing longitudinally through them. Rails in such a position influence the needle to a much greater extent than would otherwise be the case. Surveying in the presence of iron may be carried out with ap- proximate accuracy if readings are taken at every station instead of at every second station, and by taking back and foresights. In these circumstances, both back and foresight readings will be subject to the same degree of error, and, consequently, if a correct bearing of any particular line can be obtained, a fairly accurate survey can be made. Di2J of the Needle, — ^A magnetic needle does not, in our latitudes, assume a perfectly horizontal position. The inclination of a freely suspended needle is about 67* at Glasgow towards the north. The dip varies in the same way as the declination, and ranges from 75*, the maximum, to 66*, the recorded minimum at Greenwich. In mining dials this tendency is counterbalanced, so that the needle moves only 8URVETIN0, LBVELLING, AND PLANS. 465 in a horizontal plane. All needles have not exactly the same varia- tion, and for this reason it is very important that magnetic bearings made at the surface should be taken with the same compass that has been used for the undei^ground surveys. The length of needle in common use for underground work is 5| in. It consists of a strip of steel with an agate or ruby centre, and a cross-cut line marking the north-seeking end. Tn some cases a small vernier is fixed to one end, so that the bearing may be read to the nearest minute. The dial plate is usually constructed of brass, although in some instances aluminium has been used with success. The figures may be marked on this plate in various ways, according to the practice of different makers. The method of reading will be explained later. Determination of True Meridian, — To determine the true meridian, and from this the exact amount of magnetic declination, various methods may be employed, the best two being to make observations of the Pole star or of the sun. Ohservaiions of Pole Star and Sun. — ^This method is accomplished by using a theodolite and bringing the telescope of the instrument to bear upon the Pole star at stated intervals before and after its culmination. A reading is taken several hours before its culmina- tion, both on the horizontal and vertical circles of the theodolite. After a lapse of the same period subsequent to its culmination the star is sighted a second time, and a reading taken as before. The line bisecting the angle obtained by the two readings will indicate the true meridian. If the observations are taken during winter, which is the best time, the readings are taken at an interval of 11 hours 58 minutes for the Pole star.* Similar methods are resorted to of finding the meridian by means of observations of the sun. Setting ottt the Meridian Line, — In eveiy mining district a per- manent meridian line should be set out, so as to enable surveyors to determine the true meridian at any time. The best method of permanently marking out the meridian line is to insert in the ground, 4 or 5 ft. deep, a large hard stone, granite if possible, 6 or 8 ft. long x 2 ft. broad. The stone should be well faced and firmly set in cement to keep it from shifting. In the upper surface of the stone is fastened a brass plate, a foot square, let in so as to be perfectly horizontal, and on this the meridian line is shown by a fine engraved line. For practical purposes a point may be fixed at some part of the royalty, and a line laid out connecting it with some permanent point, such as the centre of the shaft, and the bearing of the magnetic with this line recorded every year or every second year ; the difference in the readings will be the amount of the annual variation.* • A Treatise on Mine Surveying, p 60. 466 PRACnOAL COAL-MININO. A very convenient method is to fix a pin in the ground on some part of the colliery which is unlikely to be affected by the proximity to underground workings, and to sight from this point a number of permanent objects within range, such as steeples, factory chimneys, etc. The mean of the angles made by the axis of the magnetic, and the imaginary lines connecting the point with the objects selected, determines the variation in the meridian in a more satisfactory manner than by relying on observations in one line only. To ascertain if there are any local attractions affecting the needle, a number of observations should be made on a straight line, the correct bearing of which is known. Colliery Plans, — A number of plans are published by the Ordnance Survey Department which are of great use in mining operations. The smallest are on a scale of 1 in. to the mile, showing the roads, railways, and chief land marks, such as farmhouses, plantations, streams, etc. The next size is 6 in. to the mile, showing every detail, such as fences and other boundaries. On these plans the levels are also marked, showing the height of various points above the mean sea-level at Liverpool. The positions at which the levels have been taken are indicated by dots, and the height marked beside them in figures, thus Q 683*3. Where these observations have mmam been made, bench marks, as they are called, are cut on the walls of ^IV buildings, pavements, etc. Their positions are indicated thus : * Oontour lines are also indicated on these plans by means of dotted lines. These contour lines indicate that each point on the line is at the same height (given in small figures within the areas thus outlined) above sea-level. This information is very useful to the mining engineer in aiding him to determine the levels of the various pits and bore-holes which may be put down on an estate, and in enabling him to arrive at a conclusion as to the best position in which to sink new shafts or to lay down sidings and other works. The 1 in. and the 6 in. maps can be obtained coloured, showing the geological formation of the various coalfields and the outcrops of the various seams, the depths of the pits sunk, the position and extent of faidts, where proved, and much other useful information. The largest scale plans published by the Ordnance Survey is 25*344 in. to the mile, or ^^nr ^^ ^^^ actual size of the district surveyed. These plans are very accurate, and show every surface-feature that was in existence at the time of the survey, together with the bench marks, etc. Unfortimately, the paper on which the maps are printed is found to contract and ex- pand considerably, and this may sometimes lead to an error, but that may be guarded against to a certain extent by using the scale printed on the plan itself in preference to a detached scale. On these sheets every enclosure is numbered, and a book of reference to these numbers is published for each parish represented, giving the SURVEYING, LBVBLLING, AND PLANS. 467 area of these enolosures and the nature of the ground, such as pasture land, wood land, gardens, etc., etc. In the latest editions of these plans the area of each enclosure is marked. The levels marked on an Ordnance Survey plan are not always correct for colliery districts, as the continual subsidence of the under- ground workings affects the surface leveL As an instance of this it was found recently, when a new survey of one of the Scotch coal- fields was made, that nearly every bench mark had subsided from 6 to 7 ft. The Ordnance Survey also publish vertical sections of the various coalfields, corresponding with lines shown in the plans, showing the seams, and horizontal sections showing the nature of the intervening strata. The smallest scale permitted for colliery plans, by the provisions of the Coal Mines Regulation Act, is ^g^oo' ^^^ ^^® working plans of collieries this scale is, however, too small, and the scale in common use is ^ in. to 66 ft. Sometimes scales of 1 in. to 66 ft. are used, but a plan of an extensive royalty drawn to that scale becomes incon- venient and unwieldy to work from. In preparing a colliery plan the first step is to make an accurate survey of the surface boundaries and determine the position of the various shafts and siuface build- ings. This is usually done with a theodolite. The details of fences, etc., may be filled in by enlargement from the 25 in. Ordnance Survey maps, but as many of these plans are very much out of date, it is often necessary to make a complete new survey of all the surface lines within the boundary. For this purpose the theodolite may be used, but where the details are somewhat intricate it is more expeditious to use the mining compass. A plan which has merely been enlarged from the 25 in. scale without check surveys cannot be relied upon when workings are being carried on near the boundaries, but it may be useful as a general plan to guide operations. The information which should be shown on colliery plans is as follows: — All underground workings showing the position of coal faces and the position of all pillars of coal ; faults and dykes show- ing the direction and amoimt of throw ; aU the air and water-eourses and the haulage roads. The* thickness of the coal should be marked at frequent intervals, and special care should be taken to indicate clearly what has been found in exploration workings. The dip and rise of the strata should be indicated with an arrow and the rate of inclination marked thereon. Levels should also be marked at various points, showing the height above a given datum line, one, two, or three thousand feet below sea-level being convenient datum lines. The date of the survey of all working faces should be neatly marked and the workings should be surveyed and extended in ink every three months. The position of all shafts should be shown and the depth marked, and a section must be given showing the strata 468 PRAOnCAL COAL-HINING. sunk through, or, if that is not practicahle, one showing the average thickness of the coal and the nature of the roof and pavement. The surface lines are usually drawn in with Indian ink, and the boundariee indicated by an edging of colour. To indicate the underground workings, colour is generally used instead of Indian ink, a separate colour being used for each seam. Faults and troubles should be shown distinctively coloured. When two or more superimposed seams are worked, and require to be shown on the same plan, each seam is coloured differently, as stated above, but it is far better to make a separate plan for each seam worked. In pillar and stall workings only the rosul need be coloured, while the solid is being worked, but after the pillars have been re- moved it is usual to colour the waste or exhausted area and show it by hatched lines. In longwall workings the waste only need be coloured and the roads left uncoloured. Roadways going through solid ooal are generally shown by unbroken lines, while those going through waste, as in longwall, are usually shown with dotted lines. The two commonest colours used in making plans are red and blue. On surface plans water is shown blue, roads ' Burnt Sienna,' and build- ings indicated in a wash of Indian ink. It is generally found sufficient to colour the roads, buildings, and water. All colliery plans should be drawn on strong mounted paper, and great care should be taken that the paper is thoroughly seasoned before being used. Undergromid Surveying. — For the great majority of underground surveys the instrument used is some form of mining compass. In cases where there is no disturbing magnetic influence, such as in sur- veying the roadway shown in fig. 488, the compass is first planted at B and then care- fully levelled, the needle being allowed to settle. A lamp is now held at A in the centre of the shaft, or on one Fig. 488. of the guides, and the sights of the compass rotated until the hair cuts the light. The bearing is then read off and recorded in the survey book, the measurement being taken at the same time by the assistants, and likewise recorded in the book. By this time a man has gone forward to the point C, and places there a lamp on the floor as near to the centre of the road as possible. The bearing from B to G is now taken and recorded in the same way. The surveyor then lifts the compass and plants it at D, and takes the bearings D C and D £ in the same way as before. There are various ways of booking a survey like this, two of the commonest methods being here shown. 8UKVEYIMO, LBVELUNQ, AND PLANS. Firtt Method 0. of Re.iring. B.«ring. Di>Unce Links. Remarks. 0) (2) I*) N. 70E. S. 8GE. N. 7SE. H. GE. 100 Frum oeutro of Ho. I 129 IS7 122 Second Method .—'With the second method it ia deBirab! 3 time as the bearings are being written a small sketch at the i down, 80 aa to give the Burvejor a general idea of the ground he is surveying {fig. 489). This is a very satis- factory and expeditious method of surveying, provided the surveyor has had eufiicient practice to sketch neatly. There are one or two points which Fio. 489. need to be taken note of. Take bearing No. 3, which reads S. 65 E. A oommou mistake among learners in marking a bearing like this would be to record it as N. 85 K, and a mistake like that is almost imposaible to oheck when the survey comes to be plotted. Take now the bearing B C, as shown on fig. 490 ; whichever end of the needle may be looked at there is only the one figure which can be read off, vis., 85*, and this ia accordingly marked in the boo^ Simi- larly the last bearing might have been marked N. 6 W., whereas in the othir case it is simply marked 176°, and it is hardly possible to make a mistake. The only mistake which is liable to occur with fio. 490. this latter method is that such a bearing as D R might have been sketched as turiii right instead of to the left. A mistake like that, however, detected when plotting, and with a little care underground i ing the general direction of the road, whether towards the towaitls the soutli, this source of error should be easily avoit It occasionally happens iliat a few bearings have to be 470 PRACTICAL COAL-MININa. Fig. 491. some point where magnetic attractions are exerted, and that a free vernier compass cannot be employed for the purpose. To do this with the loose needle the method usually adopted is shown in fig. 491. Planting the compass at B, the bearing reads 60*" from B to A and 90* from B to C. Planting again at C, a back sight is taken to B and reads 83*, and a foresight to D reads 135*. Similarly at D the back sight reads 133* and the foresight 70*, and at E the back sight is 73' and the foro- '^ ' sight is 92*. At E there is no iron to attract the needle, but as a check back sights are taken at F, and as this also records 92* it indicates that the bearing taken from E is corrects Now the bearing from £ to D is 73*, and this bearing having been taken from a point where there is no attraction is bound to be correct When the compass was at D the bearing from D to E read 70*, there- fore the amoimt of attraction at D is 73 - 70 « 3*, to be added to the observed bearing, so that the bearing 133 taken from D to C is 3* wrong and should be 136*. In the same way at C the correct bear- ing C to D is 1 36* and the compass reads 135*, — that is, l* to be added to the compass bearing, so that the correct bearing CtoBis83 + l« 84*. Again, at B the compass reads 90 from B to C instead of 84*, so that 6* must be dedttcted this time from all bearings taken at the point B, and the correct bearing from B to A becomes 54*. The survey would now be plotted : A to B 54*, B to C 84*, C to D 136*, D to E 73*, and E to P 92*. The student should never think of seeking the average bearing of the back and foresights in a survey of this kind, as such a method would be quite incorrect, and a careful surveyor would endeavour to secure a sight free from magnetic disturbance at each end of the surrey, so that the one mav be checked by the other. The Fixed Needle or Vernier Compass. — This instrument may be used in two ways iinderground. The first method is by taking the angles between each two bearing lines by placing the I'emier at zero at every station, as is sometimes done with the Uieodolite when taking a surface survey. This method of surveying is, in the writer's opinion, quite unsuitable for general underground work, and will not be further described. The second method is to take the bearings and book them precisely the same as if they were loose needle bearings. Let fig. 492 represent a working which is to be surveyed with the vernier along the road from A to F, which is laid with steel raila. Suppose that at B^ there is an old roadway without rails, and where the compass can be planted at a sufficient distance back from the SUBVariNG, LKVKLLING, AND PLANS. 471 main road to avoid disturbing influeuces. The first operation is to set up the compass at B^. Fix the arrow on the vernier plate opposite zero, then unclamp the needle, and after allowing it to settle turn thc^ dial round until the needle also points to zero. The clamp screws are then tightened to secure the compass to the tripod and the clamp- ing screw of the vernier slackened. If the dial is now turned round, the Fio. 4W2. arrow on the vernier plate still remains pointing to the north, as it will be moving along with the north end of the needle. The sights are now turned to cut the light held at B and the vernier screw is then tightened up. Before lifting the compass a lamp is placed verti- cally below the centre, and for this purpose a brass plumb line with a thin flexible cord is used. The instrument is now lifted and planted exactly abuve the lamp at B^ and carefully leveUed. The lower screws of the tripod are loosened and the compass turned to sight back to the lamp at B^. When this has been done the lower screws are again tightened up. It is evident now that the compass, as planted at B, is lying in exactly the same line as it was when placed at B^ and the arrow on the vernier plate stiU points to north. The vernier clamp screw is now slackened and the bearing B to A taken and recorded in the survey book. The bear- ing B to C is also taken, and while looking through the compass to G the vernier clamp screw is tightened. The compass is again lifted forward to 0, and before the vernier is slackened the back sight towards B is taken, so that the vernier still remains pointing to the north. The bearing C D is now taken. In the same way the bearings D £ and £ F are also taken. Suppose F is at the coal face^ and that it is possible to obtain a clear bearing at that point. The vernier may now be checked to see if it still corresponds with the needle. If it does the survey may be taken as correct, but the student will very often find that his work has not been done with sufficient accuracy, and that the needle does not coincide with the vernier. If the work is important a new survey must be made, but in many cases it will be sufficient to make an allowance for the error when plotting the survey. For instance, if the last bearing £ F in fig. 492 is 1** wrong, then this error may be divided among the total number of bearings (which in this case is five), so that 1 2 minutes would require to be added or deducted, as the case may be, in each case. It is not always possible to get a clear bearing at the commencement of the survey. In such a case the survey may be taken from the face outwards, or if that is not convenient then a start may be made at the pit 472 PRACTICAL COAL-MINING. Fio. 498. bottom the vernier' being put at the incorrect north indicated by the magnetic needle, and the survey made inwards in the usual way until a clear bearing can be obtained. If at this point the needle is, say, 5* different from the vernier, then this difference must be allowed on each bearing up to the point where the clear bearing was obtained. The vernier is then adjusted to coincide with the magnetic needle, and the survey proceeds as before. When a side road, off the main road, has to be surveyed with the vernier it is necessary to leave in two marks on the main line of survey. Suppose at B, on fig. 493, the road B D £ F has to be surveyed. The bearing A B is taken and a mark left at A., the bearing BD is also taken and a lamp planted below the com- pass at B. The instrument is now shifted forward to D, a back sight taken, and the position of the lamp at B is now carefully marked and the bearing D £ taken, and so on, till F is reached. The com- pass is now brought back and carefully plumbed over the mark left at B and the vernier fixed at the bearing A B, as before obtained. The back sight is now taken to A, the vernier undamped and the foresight taken to C, the survey proceeding in the usual way. To insure accuracy when working with the vernier a good plan is to use two tripods. The spare tripod is phmted at the point where the foresight is to be taken, and a lamp is held exactly at the centre. After taking the sight the compass is lifted off its tripod and carried forward and placed on the spare tripod, and the back sight taken to a light held exactly at the centre of the last tripod. The surveyor has then to wait until this tripod is brought forward and planted in the position for the front sight. The learner working with the vernier often makes mistakes by slackening the wrong screws, with the result that the whole work has to be done over again. Assistants, too, often lift the lamp from the back sight point before it has been looked at, with the result that the base line for the forward sight is destroyed, and part of the work has to be repeated. These mistakes should be carefully avoided. Measurements, — In surveying, lengths are usually measured by the imperial chain, which consists of 100 links, each link being 7*92 in. long, and therefore its total length is 66 ft. By adopting this unit of length, the chain is made to bear certain ratios to other standard measurements j for instance, \ chain is equal to I pole, and 1 mile equals 80 chains, and 10 chains « 1 furlong. Again, 1 acre* SURVEYING, LEVBLLINQ, AND PLANS. 473 4840 sq. yd.s., and 22^ = 484 yds. = 1 sq. chain, therefore we have 10 sq. ohuiii.s in 1 acre, and as 10 sq. chains are equal to 10000 sq. links, 100,000 sq. links are equal to 1 acre. Measurements are also made by chains 100 ft. in length; these chains are largely used in civil engineering work, and also in uietal mining districts. By using such a length of chain, measurements can be made much more rapidly, and are easier dealt with for surface surveys. The unit of measurement in ore mines is usually the imperial chain, but very often the unit is 1 fathom and a chain used 10 fathoms long. On the Continent the unit is 1 metre, which is equal to 39*37 in. The best chains are made of the finest mild steel, as with this material they can be made lights and less easily bend. There are many sources of inaccuracy which arise from using the chain, and great care has to be taken to avoid them. The chain should be frequently checked by some standard mark, as it is very liable to become stretehed, or some of the links may be bent when it becomes too short. In most large towns standard measurements are marked with brass plates on some public building. The chain should be checked at one of those standard marks, and similar permanent marks should be laid out at the colliery, so that the chain may be checked at any time and always kept correct. Care must also be taken when measuring that none of the links are interlocked, as this would also cause considerable error. Another method of measuring is by means of steel tapes. These tapes are largely used in some American mines. In Pennsylvania, tapes 300 to 600 ft. long are employed. Measurements taken in this way are likely to be more accurate than with a chain, but steel tipes must not be allowed to kink, as they are then very apt to break. The difficulty connected with tapes is the reading of them in muddy and wet mines, where they get rusted. To obviate this, small bits of brass wire, with a certain number of nicks or cuts in them, are soldered on at regular distances apart. For very correct measurements, surveyor's rods are used; these are made of lancewood, in pieces about 5 ft. long, joined together by a ' scarf ' joint. They are often used to check the length of the other measuring instruments, and are also useful for marking out a stan- dard chain. Glass rods have also been used on important govern- ment surveys. Mecuuring on the Slope. — In chain work on the slope, corrections must be made to get the proi)er horizontal measurement There are several methods of doing this, such as: (1) by ascertaining the angle of inclination; (2) measuring along the slope and making deduction from every measurement; (3) by 'stepping' the chain. When incline measurements are required to be accurately made, the angle of inclination is ascertained by a clinometer or .similar instrument, 474 PBAOTICAL COAL-MININO. and the actual horizontal measurements can be ascertained by calcu- lation from tables compiled for the purpose. Many mining compasses are fitted with an external arc for taking the angles of inclination simultaneously with the horizontal angles. The method that is most largely adopted by surveyors is to measure along the slope and make deductions for each length, ao- cording to the inclination, the amount of deduction necessary being derived from the tables. In the absence of these, the following approximate method may be employed. Example. — A seam dips 1 in 8 ; find the horizontal lengths corre- sponding to the following measurements, 360, 470, 832. Fig. 494. If L is the horizontal length required, D the measured distance on the slope, and d the dip, L = j^lfi - (^V .'.(1) L= V129600-2025 =867; (2) L= V220900-8364 =465; and (8) L= V692224 - 10816 = 826. In the above examples decimal fractions have been disregarded, although in practice they must be considered, or the result may lead to error when considerable distances are involved. Stepping the Chain. — This is a method sometimes adopted to ascertain the horizontal measurement on inclined workings, and is very expeditious, but only approximate results can be obtained, and the method should not be adopted on gradients of more than 6* ; when the inclination is greater it is too inaccurate. The method of * stepping ' the chain will be understood from fig. 495. The chain should be taken in not more than half lengths or quarter lengths, and stretched out firmly to A, say, and a cord and plumb-bob dropped vertically to B, the distance OA being then carefully measured. The same process is repeated at C and E, the distance B C and D £ being found in the same way. The vertical distances A B, CD, EF need not be measured, unless they are wanted as a check on the work. Plotting (he Survey. — The lines and angles of a survey are usually represented on paper on a very small scale compared to the original lengths and angles. The process of Fio. 496. SUBVBYING, LEVELLING, AND PLANS. 475 putting these liues and angles on a plan is termed plotting. The plotting of surveys may be divided into three different methods, viz., by means of protractors, by rectangular co-ordinates, and by chords. The first method is the one most largely used for colliery work, and can be done very accurately with a good protractor. Protractors. — There are various kinds of protractors used for this purpose, the commonest sort being a half circle with or without a movable arm.* They may be made of brass, ivory, celluloid, or white metaL The semicircle is divided from 0* to 180* in opposite directions. To plot the survey the straight side of the protractor is laid along an assumed meridian line (fig. 496), and the bearings pricked off by making a mark with a fine pencil or needle at the desired angle and numbering the bearings as they are taken off. All bearings say to south-east and north-east will be first taken off and numbered ; the protractor will then be reversed and all the bearings to south-west and north-west pricked off and likewise numbered. In laying the protractor on the meridian line its centre should be placed on some fixed point, such as the intersection of a line drawn at right angles to the meridian line, which would, of course, represent an east and west line. The first line may then be taken from this centre point to the first bearing and the distance marked off, or it is sometimes more convenient to parallel the line to a different part of the paper, clear of the bearings altogether. For this purpose two set-squares or a parallel ruler may be used, but the latter should not be used unless it is of fair size and provided with rollers. The dis- advantage of this method of plotting is that the plan gets spoiled by the large number of pencil or needle marks that woidd be required. For office work the semicircular protractor is often provided with a movable arm and a small vernier, which enables it to be used with * The protractor shown in the Hgure ia made of boxwood. A more reliabl inatiumeut is a aemioiroular protractor uiado of boru. 476 PRACTICAL COAL-MINING. great accuracy. A long steel * straight-edge ' is laid along the meridian line, and the protractor is fitted on to this with its straight side against the straight-edge. The bearings and lines can then l>e taken off rapidly and accurately by means of the movable arm, and without requiring to prick them off or mark them on the plan. The circular protractor divided to the full circle is more accurate and convenient for plotting a survey. It may be used in much the same way as the semicircle. When provided with a swinging arm the bearings can be taken off very rapidly and accurately. Another method of plotting is to use a large cardboard protractor and parallel ruler. This cardboard protractor is usually 12 to 18 in. square and divided from 0' to 360*, numbered in opposite directions. The centre portion of the cardboard is cut oitt, and the north and south line made to coincide with the plan meridian. The parallel ruler is placed on the required bearing and transferred direct to the plan. This saves much tiaie and keeps the plan free of pencil marks, which are necessary with the ordinary circular protractor. The bearings can be taken very accurately, owing to the large diameter of the pro- tractor. In the making of the Government Ordnance Survey Plans auch protractors are always used. In Scotland a method of plotting, which can be very rapidly and accurately done by what is known as a ' table ' protractor, is largely used in mining engineers' offices. This protractor consists of a large circle 2 ft. in diameter. This circle is fitted into a square wooden frame or table a, in which it revolves on a central axis h. On the inside revolving circle is fixed a circular sheet of paper or scroll plan, with the working meridian on it ; this line is made to coincide with the north and south line on the protractor. A small brass plate c, with an arrow engraved on it, is fixed to the square frame, and the bearing required is made to coincide with this arrow, the line being transferred on to the paper direct by the aid of a T-«quare laid across the protractor. The construction and method of using this pro- tractor will be understood from the illustration in fig. 497. The bearings, after being plotted on these scroll plans, are trans- ferred to the large coUieiy plans by tracing paper. A large amount of work can be done veiy rapidly by this method, and the large size of the protractor insures its accuracy. Plotting by Co-ordinates, — Where surveys have to be plotted with great accuracy, the method of using rectangular co-ordinates is to be preferred to any other. * It consists in assuming two fixed axes crossing at right angles to each other at a fixed point or origin, and in calculating the perpendicular distances, or co-ordinates^ of each station from these axes. If the true meridian has been ascertained, it may be made to represent one of the axes. In fig. 498, w^hich illustrates this method of plotting, the north and south line, and east and west drawn at right angles have been taken to represent the required axes. * A TreeUise on Mine Surveying, by Bennett H. Brougli, pp. 140-149. 8URVEYIN0, LBVBLLINO, AND PLANS. 477 Now every line that is taken in a survey will depart from the north and south line by a definite amount, according to its angle and dis- tance, and similarly it will also depart a certain amount from the east and west line. The distance that the line departs from the north and south line is termed its latitude, and the distance that it departs from the east and west lino is termed its departure. The latitude of a point may be defined as its distances due north or south of some fixed point. The distance that one end of a line is due north or south of the other end is called the difference of latitude of the 'El^I^^^^^ kff Fio. 497. ends of the line, and similarly the distance which one end of a line is east or west of the other end is called the difference of longitude of the ends of the line or the departure. The latitude =» distance x cosine of bearing. „ departure » distance x sine of bearing. To obviate the tedious process of calculating each bearing, the latitudes and departures may be taken from a book of traverse tables. The best book of tables for this purpose is that by R. Lloyd Gurden, 478 PRACTICAL COAL-MINING. in which the tables are computed for every minute of angle. The data for the survey plotted in fig. 498 were as follows : Bearing. Distance. Lntitude. Departure. Links. N + S- E + W- N. 10' E. 100 98-5 « • • 174 • •• N. ir E. 180 29 2 ■ • • 1-26 7 • • • S. 67' E. 184 • •• 52-4 123-8 • • • S. 63'' E. 186 • « • 81-8 108-6 • • • S. 20'' W. 42 • •• 89-5 • • • 14-4 S. 29*' E. 182 • • • 116-4 64-0 • ■ ■ a 42*'W. 86 • • • 63 9 • •• 57-6 s. srw. 78 • ■ ■ 1-4 • . • 78-0 N. 70" W. 110 37 6 • • • • •• 103 4 N. es" w. 106 44-8 t • • ■ • • 96-1 N. 86' W. 47 4 1 • • • • • • 46-8 N. 66'' W. 120 48*8 • •• • • • 1096 N. h2r E. 113 91 4 • • « 65 8 • ■ • Before these co ordinates can be used for plotting, tiicy must l»c reduced to total latitudes and departures. To effect this the north- ings and eastings are regarded as positive quantities, while the south- ings and westings are regarded as negative quantities, and the reduc- tions are then computed by taking the algebraical sum at each station, which from the above data would be as follows : No. Total Latitude. Total Departure. (1) + 98-6 + 17-4 (2) + 127-7 + 144-1 (8) + 76-8 + 267-4 W - 6-6 + 376-0 (6) - 46-0 + 361-6 (6) -161-4 + 426 6 (7) -225 '3 + 368-1 (8) -226-7 + •2901 W -1891 + 186-7 (10) (11) -144-8 + 90-6 -140-2 + 43-8 (12) - 91-4 - 66'8 (18) 00-0 00-0 To plot from this table, draw a north and south line, and an east and west line, making the junction of these two lines the starting point for the first station. From this point (A, fig. 498) take line No. 1 and measure off 98*5 northwards and 17 4 eastwards, making a mark at the end of these distances. From the end of distance 98-5 draw a line at right angles to north and south, and from the end of distance 17*4 draw another line at right angles to east and west, con- tinuing this line till it meets the line drawn at right angles to north and south. Join the meeting point of these two lines to the point A, and this will give the first line of the survey. The same proce- dure is followed in regard to the other lines, measuring off all the positive latitudes to the north and negative latitudes to the south, SURVEYING, LBVELLTNG, AND PLANS. 479 while the positive departures go to the east and negative departures to the west. The student will understand this method more fully if he plots down the above survey once or twice, and works out the numbers for himself. If care be taken when getting out the ordi- We^. N(yrth. EcuL South, Fig. 498.— Plotting by Oo-ordinates. nates, this method of plotting insures great accuracy, and is specially useful for important sui-face or other surveys. Plotting by Chords. — A tied survey may be plotted from one meridian, without the aid of a protractor, by using a table of chords No. Bearing. Chords, Radius =1000. Distance. (2) N. 10*' E. 174 100 N. 77° E. 1246 180 (3) s. ^r E. 1108 1.S4 (4) s. br E. 892 136 (6) S. 20^ W. 847 42 (6) S. 29** E. 600 182 (7) S. 42" W. 716 86 (8) S. 89" W. 1401 78 (9) N. 70* W. 1147 110 (10) N. 65" W. 1074 106 (11) N. 85" W. 1861 47 (12) N. 66« W. 1089 120 (18) N. 64" E. 892 118 480 PRACnOAL COAL-MININO. In the survey already shown plotted by co-ordinates, using the same data, and from the table of chords given, we would have to draw a circle on the paper, with a radius preferably of 10 in., and through the centre of the circle draw a north and south line and an east and west line. With a pair of dividers and a scale, lay off the chorda along the circumference of the circle according to the direction of the bearing. The chords being taken from a radius of 1000 would have to bo reduced by two fl decimal places to plot with a circle whose radius is 10, thus the first chord would be 1*74, the second 12-45, and so on. When the chords are al) measured off, the rest of the work is per- formed in the same way 08 when a circular protractor has been used. This method of plotting is not to be recommended for colliery surveying, as drawing circles repeatedly on the plan and pricking off the chorda would soon break the surface of the paper and spoil it. CcUctdation of Areas. — The three principal methods of calculating plan areas are : (1) by dividing the total area into triangles or squares; (2) calculating the area by means of ordinates; (3) by mechanical methods, such as measuring instruments. The areas of coalfields are nearly all calculated in acres, roods, and poles. The statute acre is equal to 10 sq. chains or 100,000 sq. links. CcUcidatum by Triangles, — The plan area may be divided into a number of triangles, either right angled or otherwise. If the tri- angles are right angled ones the calculations are much simplified. When the triangle possesses a right angle (6g. 500) the area If none of the angles are right angles, as in fig. 501, then an angle of 90* may be constructed by dropping a perpendicular pp from any apex on to the opposite side, and the area of the two triangles thus constructed may then be found separately. Or if we have two sides and know the included angle, as in fig. 502, Fio. 499.- Plotting by Chorda. then the area A = a( X sin x SURVEYING, LKVBLLINO, AND PLANS. 481 When none of the angles are known the following formula ia used for calculating the area, A=>/S(*-o)(5-6)(»-c) where S is the semi-perimeter or half the sum of the sides. If logarithms are used, the formula becomes IjogA = .:{l.>g«+Iog(#-a) + log(»-6) + log(#-0} Fio. 601, Fio. 608. In the above triangle, if the respectiye sides a, 5, and c toe 1200, 1100, and 1000 links, 6nd the area in acres, roods, and poles. Her.S=l?22±lM±10?0=ie60 2 .'. A= >/l650{(1650 - 1200)(1650 - 11OO)(10SO - 1000)} rs ^1650 X 460 X 660 x 660 = ^/266443760000 s 616800*87 sq. linka 31 482 PRACTICAL COAL-MININO. To reduce this to acres, roods, and poles, count off five decimal places thus: — 6-16809 4 0-612Se 40 24-49440 — -^i^ .*. Areas 6 acres, 0 roods, 24*49 poles. Or by logarithms Log A=i{log 1660+log(1650 - 1200) +log(l 050 - 1100)+log(1650 - 1000)} e:i{8-2l74 + 2-6632 + 2'7408+2-8129} and Log Ab6-7119, and A=615810'00 sq. links. Calculation by Ordinaiea, — ^When the area to be calculated has an uneven outline, and is not of too great extent, the method of ordi- nates may be used. It consists in running a chain line or axis through the greatest length of the area to be calculated, and taking ofisets at right angles to the chain line. The ofifoets should be taken suffi- ciently close so as to make each figure approximately a trapezoid, therefore the more offsets are taken the more accurate will the calculation become. An example will show more clearly this method of calculating areas. B 150 1650 0 182 1800 • • • ••. 1248 176 ... 1159 66 •* . 980 188 280 866 » • • 202 398 92 • • • 160 76 146 46 • • • 0 0 Fio. 604. From the above data an irregular field was surveyed by running a chain line through it from A to B, and taking offsets right and left. By referring to fig. 504 it will be seen that the first offset ou the left hand b is o, and the next 5^, 45 links along the chain line is 145, so that if we call the distance between the two offsets d, the area of this trapezoid » (2 /^__lj=»45 ( — — j = 3262 5 sq. links, and so on with the others, taking b^ and b^ for the next trapezoid. We may avoid the division by 2 for each trapezoid, by dividing the total sum of all the trapezoids at the end. Taking the offsets on the left hand SURVKTING, LKYELLING, AND PLANS. 483 side first from A to B and the right hand from B to A, we get the following : — (1) 46 ( 0+146)= 6626 (2) 848 (146 + 202) = 120766 (8) 472 (202 + 280) =227604 (4) 486 (280 + 182)=200970 (6)260(182+160)= 88000 (6)802( 0 + 176)= 62860 (7) 89(176+ 66)= 20470 (8)179( 66 + 188)= 42602 (9)687(188+ 92)= 161426 (10) 248 ( 92+ 76)= 40681 (11) 160 ( 76+ 0)= 11260 967983 + 2=488966*6 aq. links. The area would therefore he 4 acres, 8 roods, 14*84 poles. If the area to be calculated is large this process would be tedious, and areas with curved outlines can (^ten be calculated with sufficient accuracy by the process of equalising or giving and taking ; «.e. to draw a straight line through the curved boundaiy, leaving as much space outside the straight line as there is inside it. The whole area is then divided into triangles and calculated as already shown. CdUulatiofi hy InetrummU, — This method is now much resorted to in mining engineers' offices for calculation of plan areas. The instru- ment fbr measuring such areas is called a planimeteTf and for a full description of these the reader is referred to Brough's Mine Surveying, pp. 159, 160. Levelling. — In connection with colliery operations a good deal of levelling is often required, both on the surface and underground. Levelling is defined as " the art of finding the difference between two points which are vertically at different distances from a plane parallel with the horizon." To find the difference of level between any number of points three methods may be adduced : — (1) Trigonometrical ; (2) physical ; and (3) geometrical. In trigonometrical levelling the lengths and angles have to be measured, this being usually accomplished by a theodolite, but it is a method not often resorted to, except under exceptional circumstances, such as when ascertaining inaccessible points on steep mountain sides. Physical levelling is based on the change of atmospheric pressure at different altitudes from the centre of the earth, and is found by means of the aneroid barometer, which, as is well known, records the vary- ing atmospheric pressure at different heights. With an ordinary barometer the mercury column falls on ascending hills on an average about 1 in. for eveiy 900 ft. of ascent. This method is never prac- tised for ordinary levelling, but it is exceedingly useful and much used by surveyors for ascertaining great altitudes where ordinary levelling would be impossible, or in making rough preliminary surveys in new and strange lands. 484 PSA(7nGAL COAL-HININQ. Qeometrictd Uvelling is the method moet commonly employed hj Buireyore, and can be carried out with the diflferent levelliDg instni- menta in use, or by the ordinary 'spirit lerel,' whiob torma a part of < all Hucb inBtnimentB. The instrument most l&rgely oaed in Great Britain la that known aa the ' Dumpy LeveL' Fig. 605 ehowa the construction of this instrument. * A is the spirit level attached by screws at a a to the t«leeoope B C. The small circle near the object end B of the telescope represents a small tisna- verse spirit level used to show whether the cross wire of the telescope is truly horizontal. D I) is a flat bar or oblong pkte fixed on the top of the rertiool Flo. GOG. axis ^ To this bar the telescope is attached by adjusting screws d d. The hollow vertical axis turns upon a spindle fixed to the upper parallel |>late F, the spindle being continued downwards, and being attached to the lower parallel plate G by a ball and socket joint. There are four levelling screws /, by which the vertical axis is set truly vertical. The lower plate is screwed on the tripod head H. The tripod oonsista of three wooden legs similar to those on a theodolite. In some instruments a compass ia carried on the top of the plate d d for taking the bearings of lines of trial sections. The telescope ia similar to that of the theodolite, except that the diaphragm contains one horizontal wire and two parallel vertical wires, as ahown in fig. 506, It is usually 9 to 14 in. in length, the lines within the telescope being filaments of spider's web. Adjxi»Hng the Leoel. — Before proceeding to level a section of ground the temporary adjustments of the instrument will have to be attonded to each time the level is aet up in a new position. The legs of the instrument ahould be firmly planted in the ground, and the parallel plates made as horizontal as possible. The levelling of the instrumeut ia accoii _ lished by placing the telescope wiih spirit level over one pair of the levellitig screws, atid adjusting the screws by turning both in the one direction either inwards or outwards with the thumb and forefinger, till the bubble in the apirit level is brought exactly to the centre ; the telescope is now turned horizontally through an angle of 180* and put over the other pair of screws, and the spirit level adjusted as before. This may have to be repeated thi-ee or four times until the bubble in the apirit level reals exactly in the centre with the telescope turned into any poei- * J^tatiM m Mine Surveying, p. ISB. SUBYSTmO, LBVBLLINO, AND PLAK8. 485 tion. Fig. 507 shows the positions of the telescope during the adjusting process. Great care is required in levelling the instrument properly, and the operation should not he carried out too rapidly. The next operation is to adjust the tele- scope to prevent 'parallax/ that is, to move the eye-piece and to focus imtil the cross wires are seen with perfect distinct- ness.* Further adjustment may have to be made in sighting the levelling staff and repeated each time the staff is e£ifted. The nearer the object or staff the further the inner tube must be drawn out. Levelling a Section, — Levelling is of two kinds, simple and compound. Simple levelling has only one line of coUimation, whilst compound levelling entails constant changes of oollimation. Simple levelling is resorted tn when the difference in height between two points which are not far separated is required, and where one planting of the instrument will suffice. This is illustrated in fig. 508, where the instrument is placed as near as possible equidistant between A and B, the two points the difference of whose height requires to be determined. The telescope is first directed towards A, and a back 3" «4<» Position Posihon Fio. 607. e75 —A 9.^/ Fio. 508. Sight taken in which the line of collimation cuts the staff at 2*75 ; the telescope is then tunied round and directed to B, and a foresight taken in which the line of collimation cuts the staff at 9*81 ; conse- quently there is a fall in the ground from A to B of 7*06 ft. When the foresights and intermediate are greater than the back sights the ground falls ; if less it rises and will be deduced accordingly. Cfompaund LeveUing, — When a long section of ground requires to * Parallax means an tmarmU change in the position of an otjeot caused by a ehange in the position of m observer. 486 PEACTICAL COAL-MINIMa. B D Fio. 609. be levelled, the undulations of the ground muat be followed by varying lines of coUimation, according to the rise or fall in the seotion. This method of levelling is illustratea in fig. 509. The instrument is placed between A and B, aud the reading of the back sight to the staff is taken ; the telesoope is then turned and a foresight taken to B. The instrument is now moved forward to a fresh position between B and G and a heuok sight taken on to the staff B at the same position as that at which the last foresight was taken ; the telescope is again turned and a sight taken to C. The instrument is again shifted forward between C and D and a new line of coUimation obtained, the same process being repeated till the whole section is levelled. jDatum Line. — In levelling, a datum line is generally selected for reducing the levels taken by the instrument to one fixed standard or relative height above sea-level. The Ordnance datum is "the approximate mean water-level at Liverpool," and all levels marked on Ordnance Survey plans are the altitudes in ft. above this datum. It is not, however, necessaiy or usual to adopt the Ordnance datum. Any height above the Ordnance datum may be selected, but it is best to select the datum sufficiently low to be below the lowest point in the section levelled, so that in plotting the levels will all be positive. Booking the Levels. — In booking the levels various methods are employed, but the commonest and best method is as follows : — ^J*_?!^ Distance. Bemarka. Back GUgbt 9-6 8-70 mediate Sight. 8*80 7-60 6-82 6*48 6-68 4-20 8-20 • • • 7*10 6*28 4-86 8-46 8-60 8-80 8-20 Fore- sight Bise. Fall. 2-21 2-25 1-80 0*80 118 ... 0-86 1-48 1-00 0*98 1-60 0-88 1-88 0-90 020 010 0-95 0-16 0 06 Levela. Datam. linka. 100 '00 00*00 From centre of bridga. 101 '80 100-00 10210 200-00 103-28 800-00 108-12 400-00 103-97 600 00 106-40 600*00 106*40 700-00 107*89 800-00 108-99 900-00 109*86 1000-00 Opposite enghiehooaa. 111*74 110000 112*64 1170-00 Opposite shaft 112-59 1200-00 2lt from ontaide nSL 112-79 1800-00 112*89 1400*00 1 13-84 146000 7 ft. from outside rail. 18-30 4-46 18*84 4-46 14-06 0*21 0-21 ••« .». 18-84 118-84 100-00 18-84 SUBVKTINQ, LBYBLLINO, AND PLANS. 487 Tbis method of booking levels gives more aoourate results than any system. It may, however, be more compressed, as the work can be tested when the levels are reduced ready for plotting. If the sum of the back and foresights are added up, and the sum of the rises and falls also added up, then the difference between the sum of the back sight and foresight ought to be the same as the difference between the total of the rises and falls. The difference between the last reduced level and the original datum should also coincide with these two results, as shown in foregoing example. Another method of booking the levels may here be shown, in which only four or five columns are used. This system of booking is em- ployed when rapid results are required on the ground, and can be done very quickly when practised regularly, but is not a method to be recommended for students in general, on accoimt of liability to error. IiiBtniment Height Bighta. Reduced Levels. Remirki and Distanoea Datom. 62-76 12-75 8 60-00 On floor of machine honse. 8-10 64*66 On level of discharging platfornL 11-25 61*50 At peg. 0 8-70 64-06 78 78-61 J 1-86 F } 12-21 B 61-40 100 61-40 100 6-80 66-81 120 4-60 69-11 200 4-40 69-21 272 8-46 7016 808} 79-79 / 1-87 F \ 8-06 B 71-74 71-74 Fenoe 808i 808i 6*10 78-69 400 5-70 74-09 600 6-70 78-09 600 8-60 71-29 700 11-66 68-14 800 12-00 67-79 820 70-49 } 18-10 F 66-69 Loading bank. { 8-80 B 66-69 ■1 It In this method of levelling a datum is selected, as in the above at 50, the instrument is then directed to th3 staff and a back sight taken of 12-76, this is added to the datum, and will of course give the height of the instrument above the datum line. Other intermediate sights are taken and recorded in ttie same column. These are deducted from or added to the height of the instrument^ as the case may be, until a foresight marked F is reached ; the instrument being now moved, another back-sight reading taken, and a new height obtained, and the reduced levels worked out as before. 488 PRACTICAL COAL-MINING. 9 CO ean 73W 9 ..SitPQ. 5^05 ::«:-: Plotting the Levels. — When the levels are all reduced and ready for plotting, a horizontal base Une A B^ fig. 510, is drawn on the paper and the distances a 6, be, c05 70 ••. AB3a(188*05)'x(60)>= V88787-80=:196-8 ft. Ans. 8URYBTING, LEVSLLING, AND PLANS. 491 Quesiion. — A seam dips 1 in 7 towards the south. Level course is N. TO"* K ; find the true bearing of a road rising 1 in 60. Assume A C and A B to be of equal length (fig. 516). A C is level, and A B rises 1 ft in 60 ft., therefore the point B is 1 ft higher than K ^ Fio. 516. G. Now the seam is rising 1 in 7, and if it rises 1 ft from 0 to B, distance G B must be 7 ft By trigonometry sinO AB=j^=^=r01166. From Ubles sin 0'1166~6*-42' and the bearing of road= 70** - 6* 42"= N. 63* 18' B. Ana. Or let the diameter of the cirole be 120 ft, then Girciimrerenoe=120 x 8 '1416 a 377 ft neatly. and877 : 7 :: 860*=6'4r. To find bearing AB=N. 70E. .'. AB=N. 70'-6Ml'B. bK. 68M9'£. Fio. 617. Quettion. — A seam is dipping 1 in 3 due south, a road is driven N. 46* W. Find the inclination of road A road driven N. 90* W. vill be level Sin 45*= 1*4142186 If AOslOO, BOalaoslOOand 492 PRACTICAL COAL-MININO. A B= VlOO«x 100«= s,^0000=141 '42186 100 The seam is rising 1 in 8. .*. B i8^=83'8 ft above G and also 88*8 ft. aboTe 8 A ; 80 that A B rises 88*8 ft. in 141*4 ft and inclination =iil!i?=rl in 4*24. 88*8 Fio. 518. Question, — A seam is dipping 1 in 5 due south. A road is driveo N. 60* W. Find its inclination. Fio. 619. If AG»100, BC»60. .*. A B= is/lOO* x 60"s=lll'8, if B C=50 and is dipping 1 in 6 then B is ^=s 10 ft higher than 0 or than A, so that AB rises 10 ft in 5 111*8 and .*. inclination =i^^ si in 11*8 Ana. Question. — A road has been driven 1* off the bearing. Find how much it is out in 600 ft. Fio. 520. By trigonometry BCsABxsin B A 0=500 x '0176 « 8*76 ft Ana. SURYSTING, LBYKLLING, AND PLANS. 493 An approximate method of working a question of this kind, and Fio. 621. which may be useful to students who have no acquaintance with trigonometry, may be explained as follows : — Let BCD be a circle with a radiuB of 600 ft. (fig. 621). . *. The circamferenoe of tbia circle =2 x 600 x 8*1416 = 8141-6 ft Snppoee the arm A B is awnoff round a complete circle it will have described an angle of 860*, and the point d will have tnvelled 3141*6 ft. Now, by pro- pordon, if B travels 8141 6 ft for 860*, how many ft will it travel for 1* f .-. 860* : 1* x: 8141-6 ft or 1x81 41 6 860 B 8 '72 ft Ana. This distance, of course, is measared along the arc of the circle, but in a case like this the difference between the length of the arc and that of its chord is infinitesimal, and would be negligible for all practical purposes. Question. — If a road has been driven for 200 yards and A is then found to be 30 yds. off the true course, which must have been the error in bearing in setting out* Fio. 622. BO By trigonometry sin ^^-r-x ^80 200 .•.sin ^=1600 .•.^=8*88' Anst 494 PRACTICAL COAL-MINTNG. or by tbe approzimate method mentioned aboTe we hare a drole whose radina ii 200 ydi., . *. circumferenie=2 x 200 x 8*1416 B 1256 -64 ydft. Fio. 528. bat the circnmrerence is also =s 860*. .*. 1256*64 yds. : 80 yds. : : 860* 80x860^3.3^.^ • 1256-64 IN D E X. Adrlaidb drill, 94. Adit levels, 294. Adjusting serewB for winding ropes, 288. After-damp, 856. Air, composition of, 868. losses in compressing, 124. through friction, 126. moisture in, 858. Air-compressors, 121. Air-crossings, 886. Air-cnrrents, 892. formulffi for, 400, 401. guiding, 386. Air-pipes for yentilstors, 892. Air-yessels on pumpe, 841. Aitken process for timber, 200. Alluyiaf deposits, boring in, 20. Altered rocks, 2. Alternators, 129. Ammonia, use of, in freezing, 63. Ammonite, 77. Amyis, 77. Anderson-Boyes coal-cutter, 105. Anemometers, 404. Angle method of working coal, 167. Anthracite, 6. Anticlinal fold, 2, 8. Aqueous rocks, 2. Aitieer powder, 76. Argus powder, 78. Atmosphere, height of, 864. Balanoiko pump rods, 818. Banking out, 440. Barclay engine, 820. Bar coal cutting machines, 108. Barometrical pressure, 402. Barraclough pulley, 277. Barring, 48. Baah coal-washing machine, 450. Banm coal -washer, 458. Beams, calculating the strength of. 197. B^he, 16. Bedding of rocks, 2, 188. Bellite, 78. Bits, forms of, 18. Bituminous coal, 6. Black damp, 855. Blaes, 141. Blasting, 80. cost of, 84. Blasting-gelatine, 78. Blind ecu, 7. Blind pits, 264. Block Drake for drums, 288. Blowers, 858. Blown-out shots, 88. Boart diamonds, 24. Bobbinite, 72. Boghead or torbanite, 7. Bogie clips, 285. Boilers, 486. accidents to, 488. chimneys, 440. eyaporative power of, 488. Bord and pillar method of working coal, 144. Bore-holes, distance set forward, 26. lining, 18. sunreying, 29. uses of, 12. Boring by diamonds, 28. by hand-iK>wer, 25. cost of diamond, 25. cost of Jap'inese method, 20. cost of Mather k Piatt, 22. cost of spring-pole, 20. dangers attending, 26. frame, plan and elevation, 25. headgear used in, 16. in almvial deposits, 20. in hard ground, 24. in ordinary strata, 18. 496 496 IKDIX. Boring, methodi of, 18. percaanye, 18. preliminaiy operations in, 15. removal of debris in, 15. rods, 14. extracting broken, 18. rotary, 28. speed of, 20. speed of diamond, 25. speed of Mather k Piatt, 22. tools used ill, 17. URe of dinograph in, 29. chisels, 14. Bracehead, 14. Brakes, dram, 288, 284. Brake staff, 15. Brattice, 890. Briart's method of fixing guides, 225. wheel for haula^, 272. Brick drams in sinking, 48. Brickwork supports for roads, 190. Brown coal, 8. Bucket pumps, 802, 808. Buildings. See Packs, Bulldog powder, 72. Bull pnmping-engine, 819. Burnett's roller wedge, 87. Burn's brake, 284. 'Burnt 'coal, 4. Gablsb, armoured, 128. firing, 82. fixing, 128. shaft, 128. Gage, speed of, 281. pnides, 224. iron or steel, 226. props, 289. See also Kept, rope or rod, 227. wood, 224. Cages, 228. double-decked, 280. for inclined shafts, 282. safety, 287. single-decked, 229. Caking coal, 6, 7. Calorific power of coal, 9. Oambrite, 75. Cannel, 7. Capacity of pumps, 296, 817, 847. Cappell fan, 876. Capping for winding ropes, 216 et uq. Carbon, 352. dioxide, 855, 856. monoxide, 857. Carbonic acid in mines, 855. Carbonite, 75. Carburetted hydrogmi, 868. Carriage for tubs on inclines, 20S. Cast-iron props, 186. Catch blook, 284. Centrifugal fans. See Fans, pumps. See Pumps. Chain and staple balance, 219. Chain coal cntters, 107. Chain wheel for haulage, 278. Chains in measurement, 472, strength of, 218. Champion coal cutter, 118. Charles's law, 124. Chesnean fire-damp indicator, 426. Chisels for boring, 14. Chlorate explosives, 74. Chloride of calcium in freezing, 64. Choke damp, 856. Chutes, 167, 168. Circular shafts, 82-42, Circumferentor, 460. Clanny safety lamp, 416. Clarke k Steavenson coal ontter, 108. Classification of coals, 6. of explosives, 71. of rocks, 2. Clearance, loss of air by, 126, CleaU, 188. Cleavage of rocks, 2, Clinograph, 29. Clips. See Eaudage dips. Close drifts, ventilation of, 891. Clowes's fire-damp indicator, 428. Clydite, 76. Coal, analysis of, 7-9. boring, 12. calorific power of, 9. characteristics of, 6. classifications of, 6. definitions of, 6. formations of, 5. in other formations than the Carboniferous, 5. in New Sonth Wales, 6. rocks associated with, 5. Coal-cleaning arrangements, 447-459. Coal-cntting by machinery, 97-118. Coal-ontting machines, chain, 106. classification of, 99. choice of, 114. conditions suitable for, 116. Disc, 100. Gillott & Copley, 100. Harrison, 112. Ingersoll-Sergeant, 111. Jeffrey, 107. g)wer for, 117- igg k Meikl^ohn, 101, INDEX. 497 CkMl-ontting machines, Stanley, 99. SnlliTao, 11^ Goal meaeuree, 5. Goal-screening, 447. fixed inclined screen, 447. rerolying, 448. shaking or Jigging, 448. Goal tar for timber preservation, 201. Goal washing, 448. Goffering, 41. GolUery plans, 466. Gompasses used in snnreying, 460 et seq. variations of, 461, 462. Gompressed air, 121. m sinking, 68. Gompressed air, losses in, 129. Gondnctors. See Guides. Oonqueror drilling machine, 91. Gores in boring, 23. Gomish boilers, 436. engines, 819. Gorves, 248. Gost. See under Boring, Coal euUing, Goonterbalancing, 219. chain and staple, 219. pnmp rods, 818. tail rope, 220. Greep, 147. Greosote for preserving timber, 200. Grown, diamond, in Irariog, 28. Grow's-foot grapnel, 18. Grush, 147. Dahmenitx, 78. Darlington drill, 98. Datum line, 486. Davey*8 differential pump, 826. Davy's, Sir H., safety lamp, 416. Definition of explosives, 71. Detonators, 79. Devonian formation, occurrence of coal in, 6. Diamond boring, 28 it seq. cost of, 26. Dip, angle of, 2, 8. Direct-acting steam pumps, 818. Direct rope haulage, 266. Double-decked cages, 280. Double plunger pump, 346. Double stall system, 171. Down-throw fault, 8. Drift process of coal formation, 6. Drilling, cost of, 92. Drilling machines, Adelaide, 94. Gonqueror, 91. Darlington, 98. Ingersoll, 96. Drills for rocks, 91 hand, 91. machine, 92. ratchet, 91. Drum, distance of, from centre of shaft, 210. See also fFinding, Drum brakes, 238. Drum, methoid of sinking, 48. Dry compressors for air, 121. Duty of pumping engines, 848. Dykes, 3, 4. Dynamite, 74. Dynamos, 129. Eabth*8 crust, composition of, 1. Efliciency of electrical transmission, 181. Electric detonators, 86. lamps for mines, 426. Electrical terms, 186. Electricity, firing shots by, 81. for power transmission, 127. haulage by, 182. pumping by, 188. Electronite, 78. Elevators, 446. Elliot's coal washer, 461. multiple wedge, 87. Elliptical shafts, 81. Endleas rope haulage, 76 et seq. cost or, 290. Engines. See Haulage enginee, Pump- ing engines, H^inding engines. Equivalent orifioe^f mines, 381. Evan's safety lamp, 422. Evaporative power of fuel, 10, 1 1. Expansion joints for pumps, 297. Explosive gases in mines, 367 el seq. Explosives, 71-79. blasting gelatine, 78. chlorate mixtures, 78. classification of, 71. dynamite, 74, gunpowder, 72. fist of permitted, 76. nitro-compounds containing nitro- glycerine, 78. not containing nitroglyoerine, 77. safety, 74. selection of, 74« various patent, 76. Fakb, 878. Gappell, 876. compressing, 880 cost of, 386. dimensions of, 880, 882. 32 498 INDIX. Fans, Onibal, 878. quantity of air deliyend by, 882. Schiele, 875. selection of, 879. speed of, 886. temporary, during shaft sinking, 68. Waddle, 875. Walker, 877. Faults, 8, 4, 13. Faversham powder, 78. Felspar coal washer, 456. Fire-damp, 868, 861. detection of, 362. explosions, precautions against, 80. Fish-plate for iron sets, 188. Fisher's clips, 282. Fissures, 8. Flame communication, 84. Flaming; coal, 7. Formation of coal-fields, 5. Formulie for air-currents in mines, 400, 401. for fan ventilation, 882. for gradients, 263, 264. for haulage problems, 292, 298. for pumps, 817, 846. for sizes of pipes, 299. for sizes of pump-rods, 809. for sizes of ropes, 217, 218. for size of winding-engine, 244. for strength of chains, 219. Freezing, methods of sinking by, 62, 68. tubes used for, 68, 64. Friction detonators, 80. on nils, 248. Fu^, evaporative power of, 10. Furnace ventilation, 866 et seq. Fuses, safety, 80, 81. Galloway's scaffold, 86. doors for sinking, 46. Garland, 88. Gas ooal, 6, 7. Gas vents, 868. Gases in mines, 860 d seq. carbon dioxide, 856, 856. carbon monoxide, 857. carburetted hydrogen, 868. sulphuretted hydrogen, 858. Gauge for haulage roads, 248. Geared pnmping-engines, 818, 822L Gelatine, blasting, 78. dynamite, 74. Generators, electric, 129. Gillott and Copley coal cutter, IOOl Girders for rosd supports, 190. Glands for pit-head fhuBM, 90ft. Goaf, 140, 149, 177. Gobert*8 method of sinking, 92, Goolden bar machine, 109. Gore pit, 188. Gradients, formnlte for, 258, 264. Oradins Ren^Knis, 169. Gray safety-lamp, 419. Grooved pulleys, 278. Guibal fan, 878. Guides, Briart's method of fixing, 826. for cages, 224. iron and steel, 225. rope. 227. wood, 224. Gunpowder, 72. Gywnne pump, 887. Hadx, 8. Hand drills, 91. Hang-fire shots, 81. Hanging scaffold for lining, 84. Hanson clips, 288. Haulage, 247-298. arrangements at pit-bottom, 253. automatic detacher, 282. bnke arrangement, 289. branch roads, 269. Briart's wheel, 272. by stationary engines, 265. carriages for tubs, 265. chain-wheel for, 271. cost of various systems, 289. direct rope, 265. driving pulley, 277. formulae for gndienta, 268, 264 horse roads, 258. horse traction, 262. laying roads for, 218. manual labour for, 252. main and tail rope, 266. staple pits, 264. tubs, 268. working branches, 269. working curves, 274. working landings, 288. Haulage clips, 280. bogie, 285. Fisher's, 282. Hanson's, 288. Hnmble's, 288. Rutherford and Thomson's, 284. Smallmau's, 288. Ward and Lloyd's, 284. Haulage engines, 266. See also Snginu, Haulage inclines, 256. cut-chain, 268. self-acting, 266, 262. IMDKX. 499 Haulage pulleys, 277, 278. Briart'i, 272. roller, 28d. Haalage roadi, catch block for, 234. rulB for, 247. Haalage ropes, guides for, 267, 268. knock-ofis, 267. pulleys for, 277. shackle for, 268. speed of, 271, 279. tightening, 279. Haulage systems — endless ehain, 271. endless rope, 276. main and tail rope, 266. Heading machine, 99. Heenan k Froude's rotary tippler, 444. Height of atmosphere, 854. High ezplosires, 71. High-lirt centrifugal pump, 837. Holing (ax>p6, 140. Hooks, King and Hamble's, 236. WalkeA, 285. West's, 236. Horisontal pumping engine, 321. Hordes, keep of, 254. stables for, 255. Hamble*s clips, 283. Humus in relation to origin of coal, 6. Hurd bar machine, 109. Hurdle screens in veutilation, 391. Hutches, 248. Hydraulic keps, 242. pumps. See Pum]n» Hydrogen, 352. loNBOUS rocks, 2. Inclined seams, 159. Inclines. See Haulage indines. Induction currents, 463. Ingersoll drill, 95. IiigersoU -Sergeant coal cutter, 111. Injection compressors, 122. Iron and steel road supports, cost of, 186 it $ea. Iron eyliuders used in sinking, 49. ffuides, 225, 226, 227. leps, 289. kibble, 65. pithead fimmes, 202. props, 86. riders, 66. ropes for winding, 212. seta for roads, 186. supports for roads, 186. tubs, 248. Japanbsb kettle catch, 20. method of boring, 20. Jeffrey coal-cutter, 107. Jig brow haulage tackle, 256. Jiggers, 280. Jizai Kagi, 20. Jointing, 138. Junction boxes, 129. Jurassic formation, coal found in, 6. KaskIiOWbkt pump, 832. Keps, 239. hydraulic, 241. Stauss, 239, 241. Kibbles, 65. Kieselguhr, 74. Kind-Ghaudron system of sinking, 54. Kind's plug, 19. King and Humble's hook, 236. Koepe's system of winding, 221. Kriickel, 61. Kynite, 76. Laboitb for machine cutting, 116. Lagging, 182. Lamination of rocks, 2. Lamps. See Safety lamps. LeTelling, 483. lifts, length of, in pumps, 316. Lignite, 6, 8. Lipes, 175. Lippman's method of sinking, 59. Longwall method of working, 187, 149. length of walls, 139. ripping, 189. spragging, 140. widtn of roads, 139. working thin seams, 142. See also Methods of IVorking, Loose ground, driving through, 182. Lilhrig and Copp4e coal washing ma- chines, 454. Machinx drills. See Drilling ma- chines. Machines, boring, 91. coal-cutting. See Coal-euUing marines. winding. See Winding machines. Magnetic declination, 461 ei seq, dip, 464. meridian, 461. needle, 460. ridge lines, 461. storms, 464. Main and tail rope haulage, 266. Mains, electric, 127. Mammoth pumps, 66. 500 INDEX. Maraant safe^ lamp, 817. Marah gas, 868. Masonry lining for shafts, 84. Mather k PlaU system of boring, 21. Mather k Piatt's pamp, 837. Measurements, 472. Mechanical coal cutters, 98. veutiiation, 373. wedges, 87. Metamorphic rocks, 2. Methods of sinking by bribk drums 40. Gobert's, 62. iron cylmders, 49. Kind-Chaudrou, 64. Lippmann, 69. pile-driving, 47. Poetsch, 64. special, 47. Triger. 68. Methods or washing. See CocU uxuA- ing. Methods of working, angle, 167. bord and pillar, 144. double stall, 169. longwall, 187. panel, 161. pillar and stall, 144. single stall, 169. special, 162. stoop and room, 144. thick seams, 172. vertical seams, 163, 166. Millstone grit, 5. Mine gases. See Ocuet in mines, Minex«ls associated with coal, 6. Miocene deposits of ooal, 6. Miss shots, 81. Moisture in air of mines, 868. 'Monkey' knock-off, 268, 270. Moor rock, 6. Moore's hydraulic pump, 381. Mobs box, 67. Moss, wet, for oartridges, 84. Motors, electric, 180. for compressed air, 121. Mueseler safety lamp, 418. Murton coal washer, 451. Mushroom Talve for compressors, 124. Nbw South Wales, coal in, 6. New Zealand, coal in, 6 Nitro explosives, 71 Nitrogen, 862. NobelArdeer powder, 7C carbonite, 76. Non -caking coal, 6, 7. Oak curbs for lining shafts, 82. Ordnance datum, 466. Origin of coal, 6. Outcrop, 2. Overwinding, automatic apparatus for preventing, 243. prevention of, 234. Oxygen, 362. Packs, 189. Panel system of working, 161. Parrot coal, 7. Pattberp system of sinking, 69. Percussive boring, 18. machines, 109. Permitted explosives, list of, 76. Pieler fire-damp indicator, 424. Pile driving, 47. Pillar and stall method, 144. direction of pillars, 148. mode of extracting pillars, 149. siie of pillar, 147. width of stall, 148. Pipes. See Compressed air, Pumps. Piston pumps, 324. Pit-bottom, arrangement of, 251, 253. Pithead frames, 202. glands for, 206. Pithead pulleys, 231. Plant, electric failures, 181. Plotting, 474 et seq. Plunger pumps, 816. Poetnh's method of sinking, 64. Power, transmission of, 119. by oompressed air, 121. electricity, 127. hydraulic power, 119. rods, 119. steam, 119. wire ropes, 119. cost of various systems, 136. Preservation of timber, 199. Pressure of air in shafts, 866. Problems in surveying, 488. Props, steel, 186. See also K^m. Protector locks for lamps, 429. Protractors, 476. Pulleys, haulage, 277, 278. pit-head, 281. Pulsometer pump, 884. Pumping, 294. adit levels for, 294. by tanks, 294. electric, 133. siphons for, 296. Pumping engines, 818. Bull, 819. Oornish, 819. IND8X. 601 Paropin^-eDginea, direct-nctiog, 821, 822. duty of, 848. geared, 822. Pamp-rods, 804. t)ang-piece8, 811. cleats, 810. connections, 811. counterbalancing, 818. formnle for sizes of, 809. guides for, 810. method! of balancing, 809. West and Darlington's balance, 814. Pumps, 296. air vessels for, 841. arrangement of, 844. bucket, 802. calculation of capacity of, 817. capacity of, 847. oentrifogal, 886. DaTcy's differential, 826^ double plunger, 845. duty of, 848. expansion joints for, 297. fittings for, 804, 818. formme for sises, 317. hydraulic, 881. Kaselowsky, 882. length of lift, 816. length of stroke, 817. piston, 824. pipes for, 297 et seq, plunger, 316. pulsometer, 834. Riedler's, 826. Riedler's differential, 820. ■inkinff, 889. sizes of pipes for, 298. speed of, 817. steam, direct-aotinff, 818, 326. supports for pipes for, 298. thicKuess of pipes for valves for, 800. See also Falves. Bails for haulage roads, 247. supports, 187. influence of, on magnetic needle, 464. Rectangular shafts, 48. RerersM fault, 4. Rbeinpreuasen Colliery, 60. Riders for kibbles. 66. for wood oonauctors, 67. Riedler's pump, 826. differential pump, 329. valve for compressors, 128. Rigg k Meikl^ohn machine, 101. Ring curb in sinking, 88. Ripping, 141. Roads, brickwork supports for, 190. iron supports for, 186, 190. securing, with masonry, 192. supporting;, 180. width of, m long wall, 189. Roaiiways, timbering, 180. Robbing pillars, 149. Robinson washer, 458. Roburite, 78. ' Rock.' definition of, 1. Rook drills. See DrUls. Rocks, cleavage of, 2. division of, 2. stratification of, 2, 4. Rod guides, 810. Rods for boring, 18. power transmission, 119. Roofs, good and bad, 175. Ropes, flat steel, 218. iron, 218. wire, 218. adjusting screws for, 288. cappings for, 215. care of, 214. counterbalancing, 219. life of 214. size of, 217. spring coupling for, 228. strenffth of, 216. tests for winding, 214. weight of, 218. See ffauioffe, Wvnding, Rotary borine, 28. Rotaxy wheelcoal cutters, 100. Rutherford and Thomson's clip, 288. Safstt caoes. See Co^m. Safety explosives, 74. Safety (uses, 80. Safety hooks for winding. See SookM, Safety lamps, 416-434. Ohesneau indicator, 425. Clanny, 416. Davy, 416. electric, 426. Evan, 422. fire damp indicators, 428. Gray, 419. hydirogen indicator, 428. Marsaut, 417. Mueseler, 418. Pieler indicator, 424. Stephenson, 417. Stokes' indicator, 426. Thomas s, 422. 502 INDSZ. Safety lamps, Wolf, 420. Woir-DahlmaDD, 421. cleaning, 488. construction of, 427. cost of upkeop, 428. definition, 416. filling, 484. lighting, 484. lighting power of, 427- locking contrivances, 429. protector lock, 429. testing, 480. trimming, 488. Safety riders, 67. Sand, wet, for cartridges, 48. Scaffold, Galloway's, 36. hanging for Uniug, 84. Schiele fan, 875. Scotch cannel, 7. Scotland, Garhoniferons formation in, 5. Sedimentary rocks, 2. Setting props at face, 177. Shackle for haulage ropes, 268. Shaft, ascertaining centre of, 210. cables, 128. Shafts, sinking of circular, 88-48. enlarging, 69. fixing steam pipes in, 120. form of, 81. oak curbs for lining, 88. sites of, 81. size and numlier of, 81. temporary lining of, 82. yentilation of, during sinking, 68 wood lining for shafts, 48. sinking, 80. accessories to, 65. fixing timber, 43. Galloway system, 85. temporary lining for, 88. Short-circuiting, 127. Shot firing by electricity, 81. Siding accommodation, 435. Single decked cages, 229. Single stall, 169. Sinking by freezing, 62, 68. methods of. see Methods. preliminai^ operations, 32. pumps. &do rumpe. scaffolds, 85, 86. speed of, 48. Sinking and walling simultaneously, 85. Sinking wall, 62. Siphons, 295. Sleeve for road supports, 189. collar in boring, 22. Sliding joint for boring tools, 18. Sludgers, 15. SmalTman's dip, 288. Smokeless coal, 6. Sole-piece for rail supports, 191. Specific grayity, 351. Spears. See Pu7rq> rodi, Spragging, 140. Spray compressors, 122. Spring attachment for winding ropes, 228. Spontaneous combustion, 157. Spouts, 161. Square work, 172. Stables, 255. Stage compression, 121. Stanley heading machine, 99. Staple pits, 266. Stauss keps, 289. Steam, losses in underground convey- ance of, 120. use of, underground, 119. Steam pipes, fixing, in shaft, 120. Steam pumps. Sm Fumpi, Steel props, 185. rails for road supports, 186. cost of, 187, 188. ropes for winding, 212, 218. sets for roads, 180. tubs, 250, 251. Stephenson safety lamp, 417. Stepping the chaiUj 474. Stokes's fire-damp indicator, 426. Stone coal, 7. Stoop and room working, 144. Strata, dislocation of, 8. inclination of, 2. Stratified rocks, 2. Strength of pillars, 195. Stroke, 8. Stythe, 855. SuUiran machine, 112. Sulphur, 352. Sulphuretted hydrogen, 358. Surface arrangement, 435-459. Surveying, 460-495. bore nolea, 29. definition, 460. Sussman electric lamp for mines, 426. Symbols, 851. Synclinal fold, 8. Tail rope, counterbalandng, 220. Taped cables, 128. Tapping waste workings, 26. Temperature at centre of eartli, 1. Temporary lininff for ihafts, 82. Tenacr roois, 175. INDEX. 603 Terms, electriofil, 186. Tertiary depositB of coal, 6. Thick Beams, working, 172. Thomson's ealorimeter, 10. Three^iored cables, 128. Throngbers, 161. Timber, cost of, 184. crashing strains, 196. formala for strength of, 108. tensile strength of, 197. preservation of, 199. preservation by Aitken process, 200. preservation by creosote, 200. preservation by coal tar, 201. preserved, dnrnti3n of, 201. specific gravity of, 196. varieties of, 177. Timbering, 176, 184. at face, 177. at machine face, 116. Continental methods, 181. roadways, 176 e< aeq. See also Spragging^ Boadx^ gtc Tipplers, 442. rotary, 442. Tonge's hydraulic cartridge, 89. Trams, 250, 261. Transmission of power. See Poioer. Trap doors for ventilating currents, 887. Trap doors, automatic, 888. Travelling belts, 444. Trepans, 66, 67. Triger*s method of sinking, 68. Trough ooal-washing machine, 461. Trough fault, 8. Tubbing, 88. oorrosion of, 41. formulsB for finding thickness of, 40. Tubes for lining bore-holet, 18. Tubs, 248 it aeq. UirDiROKOUND cables, 128. Underground surveying, 460. Unstratified rocks, 2. Upthrow fault, 8. Valyx-oeab, Davey*8 differential, 826. Vees, 8, 18. Yentilation, 860-414. air crossings, 886. air currents, 392, 400. air pipes, 892. Ventilation by fiilling water, 866. by fans, cost of, 870. brattices used for, 890. dose drifts, 891. during shaft-sinking, 68. fumaoe, 866. cost of f\iel for, 870. problems, formuln for, 367, 869. guiding currents, 886. urdle screens, 892. natural, 864. position of furnace, 872. problems, fans, 382. size of &n required, 882. speed of air in upoast, 372. trap doors, 887. See also Fana. Vernier compass, 4'JO. Vertical Cornish pump, 841. Vertical seams, working of, 162, 169. ViBor, 248. Voltages, 129. Waddle fan, 874. Walker's detaching hook, 286. Walker fan, 377. Walling crib or cradle, 84. roads, 184-196. cost of, 184. Ward and Lloyd's clip, 284. Washiuff ooaK 448-469. basn washer, 460. Baum's, 468. Elliot's, 461. felspar, 466. Ltthrig ft Copp^'s, 461. Murton's, 461. Robinson's, 468. trough, 461. Water cartridge, 89. cart, 409. ring, 88. tapping waste for, 26. vapMDur in air of mines, 353. Wedges, mechanical, 87. Burnett's, 81. Elliot's multiple. 87 West's hook, 236. Westfalite, 79. Wet compressors, 122. moss for cartridges, 84. sand for cartridgis, 84. Wliite damp, 867 Winding, 202. Koep4's system, 221. Winding drums, 232. Winding engines, 207, 248 504 INDBX. Winding engines, position of, 210. seats for, 212. speed of, 210. Winding ropes, 212, 216. dressings for, 215. life of, 214. Inbrioating, 214. quality of wire for, 218. Wire ropes. See Itopea, Wolf safety lamp, 420. Wolf-Dahlmann safety lamp, 421. Wood ohooln, 178, 179. for pithead frames, 202. gniaes for cages, 224. preparation of, for lining, 46. Wood and Burnett's rotary tippler, 442. Wooden kibbles, 66. rods for boring, 14. tubs, 250. 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Tbxv-Book*' wot dmigmd 6y ProfaMor BAsannB m an Istbo- Doonov NTENTS — Early History of Pnmpinff En^es — Steam Pnmping ESngines — Pnmps and Pomp Valyea^Greneral Prinoiples of Non-RotaliTe Punpiag Engines — The Cornish Engine, Simple and Gomiponnd—l^nP^ ^ Mining Engines — Pit Work — Shaft Sinking — Hydraulic Transmission of Power in Mines — Electric Transmission of Power — Valve Gears of Pnmping Engines — Water Prebsnre Pumping Engines — Water Works En^es — Pnmping Engine Economy and Trials of Pntnping Machinery — Oentnfngal and other Low-Lift Pumps— Hydraulic Rams» dumping Mains, &a— Lissx. ^*B7 the *one Saglitli Sngtneer who probably knows more abont PomptBg HSfOhinenr than AHT OTKSB.* ... A. voLUMS asooBDnra trk kbdltb or x.o«e Bxraiimoi Ain nuDT.**— 9nk< En^tmtet, MUndoabtedlyTHS bbst ahd most pbactioal tilxatiss on Pnmping Maohineiy tmmx ias nz Bsair rumuaaaD/'^Mininff Journal. UNDON: CHARLES GRIFFIN A CO.. LIMITED. EXETER STREET. STRAND NAVAL ARGHITECTURE. 37 At Prbss. In Larire 8vo. Handsome Cloth. Profusely Illnstrated. In Two Volumes, Each Complete in itself, and Sold Separately. AND CONSTRUCTION OF SHIPS. By JOHN HARVARD BILES, M.Inst.N.A., Professor of Naval Architecture in Qlaigow tJniTersity. CoKTEKm OF VoLUHft L— PART I. : General ConsideratUms.— Methods of Determin- aUon of the Yolunie and Centre of Gravity of a known Solid.' -*- Graphic Bules for Integration.— Volmnes and Centre of Gravity of Volumes.— Delineation and DescriptlTe GeometiT of a Ship's Form.— Description and Instances of Ship's Forms.— Description of types of Ships. Part II. : Calculation of Displacement, Centre of Buoyancy and Areas.— Metacentres.— Trim.— Coefficients and Standardising.— Results of Ship Calcula- tions.—Instruments Used to Determine Areas, Momenta, and Moments of Inertia of Plane Curves.— Cargo Capacities.— Effects on Draiufat, Trim, and Initial Stability due toFloodlngCompartanents. — Tonnage.— Freeboud.— Launching.— Application of the Integraph to Ship Calculations.— Straining due to Unequal Longitudinal Distribution of Weight and Buoyancy.— Consideration of Stresses in a Girder.— Application of Stress FormuifB to the Section of a Ship.— Shearing Forces and Bending Moments on a Ship amongst Waves. — Stresses on the Structure when Inclined to the Upright or to the Line of Advance of the Waves. — Distribution of Pressure on the Keel Blocks of a Vessel in Dry Dock.— Consideration of Compression in Ship Structure. BY PROFESSOR BILXB. LECTURES OM THE MARINE STEAM TURRINL With 181 l/iuatrationa. Price 6b, net See page 28. ffsfo/ 900, Hmd9omo Gtoth. With numorouo UluBtratlona and Tabloo. 28%. THE STABILITY OP SHIPS, BT SIR EDWARD J. REED, K.C.B., F.R.S., M.P., aaoMT or tub impxeial osobss of st. tTAHiLAUs or sussia; FBAMcas josmpH or AumiA; MBDjron or tukicby; and kxsino sum or japah; n^ UDBMT or rat iNtTrnmoM or natai. AauuTiCTs. " Sir lowASD Rsbd's ' Stabiutt or SHm' is mrALVAaLB. The Naval . win find hraoght together and ready to his hand, a mass of infonsation which he ti wiM haw to seek m an almost eadicM taiiety of pablkatMBs» and umm of wldck ho would possibly not be able to obtain at all etsewhsra.*— flftwawAj^. LONDON : 0HARU8 8RIFFIN « C0« UMITED. EXETER STREET. STRAND 38 \JHARLB8 GRIFFIN A 00:8 PUBLiCATlOMi, WOBKS BY THOMAS WALTON, NAVAL ARCHITECT. Third Edition. lUuslrated with Plates, Numerous Diagrams, and Figures in the Text. i8s. net STEEL SHIPS? THEIB CONSTBUCTION AND MAIirTENANCB. A Manual for Shipbuildera, Ship Superintendenta, Students, and Marine Engineers, ' By THOMAS WALTON, Naval Architect, AC7TH0K OF "KNOW YOUR OWN SHIP." Contents. — I. Manufacture of Oast Iron. Wrought Iron, and Steel — Com- poflitioB of Iron and Steel, (Quality, Strengtn, Tests, &c. II. Classification of Steel Ships. III. Considerations in mAlrincr choice of Type of Vessel — Framine of Ships. rV. Strains experienced by Shii>s. — Methods of Computizig ana Comparing Strengths of Ships. V. Construction of Ships. — Alternative Modes of Construction. — Types of Vessels. — Turret, Self Trimming, and 'Tmnk Steamers, &c. — Rivets and Rivetting, Workmanship. VL Pumping Arrange- ments. Vn. Maintenance. — Prevention of Deterioration in the Holla of Ships.— Cement, Paint, &c.— Index. ^* So fhorooffh and well written is ever^ every chapter in the book that it ia difficult to seleet ooal praise. Altogether, the work ' will prove of great value to those for whom it is intended."— 2%« Bnginur. anv of them as being worthy of exoeptional praise. Altogether, the work ie ezoeUent, and At Press. In Handsome Cloth. Very fully Illustrated. PRESENT-DAY SHIPBUILDING. For Siiipyard Students, Siiips' Officers, and Engineers. By THOS. WALTON, Author of "Know Your Own Ship." OsNSRAL Contents.— Classification.— Materials used in Shipbuilding.— Alternative Modes of Construction. — Details of Construotion. — Framing, Plating, Rivetting, Stem Frames, Twin- Screw Arrangements, Water Ballast Arranffementa, Loading and Discharging Gear, &c. — Types of Vessels, including Atlantic Liners, Cargo Steamers, Oil carrying Steamers, Turret and other Self Trimming Steamers, &c.— Index. Ninth Bdition. Illustrated, Handsome Cloth, Crown Svo, 7s, 6d. The Chapters on Tonnase and Freeboard have been brought thorouffhly up to date, and embody the latest <1906) Board of Trade Reffulatlons on these subJeets. KNOW YOUR OWN SHIP. By THOMAS WALTON, Naval Architect. Special ty arranged to suit tiie requirements of Ships' Officers, Shipowners Superintendents, Draughtsmen, Engineers, and Others, C0NTEKT8. — Displacement and Deadweight. — Moments. — Buoyancy. — Strain. — Structure. — Stability- — Kolling. — Ballasting. — Loading.— Shifting Cargoes.— Bffect of Admission of Water into Ship.— Trim Tonnase.— Freeboard (Load-lineX— Calcnlattons.— Set of Calculations from Actual Drawings.— INDEIc. " The work is of the liishest Talue, and all who go down to the sea in shipe should make them- selves acquainted with it?'— SMp^ng Worid (on the new edition). lONOON : CHARLES GRIFFIN A CO., LIMITED. EXETER STREET. STRAND. NAUTICAL WORKS. 39 GRIFFIN'S NAUTICAL SERIES. Edited bt EDW. BLAGKMORE, Muter Mariner, Flret Claie Trinity Honee Certlfloate, Ano& Init. N.A. ; Ahd WBimni, KAIHLT, Xtf 8AILOB8 ft» 8AILOB8. "THIB ADMnUBU OIUIB."— ^flrfrptey. '*▲ TUT USIFDL SBBIK."— JTaeiirv. '*BvBBT Ship aboiild have tlie wholi BnuK ae % iiMnxncm Ijbraet. Habb< MMiLT BOUND, OLBABLT pioiTBD and ILLUSIBAZID. "^XiMtyooI Jowm, ^ Cmnmsrm, The British HereantUe Marine: An Historical Sketch of iti Biae uid Derelounent. Q7 tbe Bditoe, Car. Blaokmorb. fla.6d. "Captain Blaokmore • bplbndib book . . . oontalna i»aragrai»ha on eTety point offinteiest to the Merchant Marine. The 248 pagea of thla book are THB worn YALU* ABU to the lea captain that have Bnni been OOMPIUD.''— jr«f«JUm< Smiiw iZM»«w^ Bementary Seamanship. By D. Wilson-Babkbb, Master Mariner, r.B.&]L, F.ILO.S. With nnmerooa Flatea, two in Coloun, and FKmtiipieoe. FovBtH BDinoH, Thoronghlj SeTiaed. With additional lUnatratloni. fla. «Thia apmibablb manual, by Capt. Wilson Babub, of the * Woioeater,' leemt to na PBBIBOKLT DBBiaNBi>."--ZeAenLAw. Oeneral Contents.— The Qnallllcetion for the Position of Shlpmsster— The Ooo- tmet with tlM Shipowner^The Master's Duty in respect of the Ciew : Sngunmeat Ijpmntless: Discipline ; Provisions, AooommodaUon, and liediosl Comforts ; Pajmsnt of wsges end Dischsrse— The Master's Dater in respect of the Pswengers The Msster^s TinaDdal SesponsibiUtise— The Msster's Dnty in respect of the Cargo— The Mssterls Dntj in Csse of Casnaltr— The Msster's Duty to oertein Pabllo Anthoiltles— The Msster's Daty in relation to PUots, Signals, Flsas, and Lia^t Dnes— The Msster's Dntf upon Arrival at the Port of Discharge AppencUoss relative to certain Legal Matten : Board of Trade Certlfloates, Dieterr Scales, Stowsge of Grain Cargoes, Load tine Segnla- tlotts. Life-saving Appliances, Canisge of Cattle at Sea, *c, dc— Copions Index. "No intsnigeat Master ahcnld fldl to add thii to hl« list of nwnewsry hookfc Afsw lines sf It msy sava ▲ Lawna's na, aasmas avoLsse woaaT. **— ^Mrpeol JennNri ^ Cbwwirw. "Sanma, nieinly written, In otsAa end vov-«bcbvxoal LAVooaei, end wiU be ftnad of ■uoB saaviOB by the Shipmstter."— ik^iiA Tradk ReHtm. Second Edition, Revised. With DiAgnune. Prioe 2e. Latitude and Longitude: Elovr to Find tl&exn. By W. J. MILLAR, C.R, '* OONOISBLT and gleablt wjuttxh . . . cannot hat prove an lo thoee stodving Navigation. "—Jlfartne Bngineer. ** Yoong Seamen will find it bahdt and nsimL, sixflb and asMAR/*—Tkt jHi^ifieei^. FIRST AID AT SEA. Tbibd Edition, Revised. With Coloured Plates and Nnmeroiii lUnatra- tions, and oomprising the latest Regulations Respeoting the Carriage of Medioal Stores on Board Ship. Prioe 6s. A HEDIGAL AND SDRGIGAL HELP FOR SHIPMASTERS AND OFFICERS IN THE MERCHANT NAVY. Bt WM. JOHNSON SMITH, P.RO.S., Principal Medical Ofllcer, Seamen's Hospital, OreenwIalL *,* The attention of ell intersstad in oar Merchant Navy ie reqaested to fhia eaoeedincty naefal and valoahle work. It le needlees to say that it ii the oatoome of many yean FBAonoaL axmuaacB amongst Beemeo. " Souan, JUDiaouB, sballt kbuvdl.'*— TA< Lamett. *«* For Complete List of Gbivtik's Nautioal Ssbib, see p. 39. LONDON : CHARLES GRIFFIN « CO.. LIMITED, EXETER STREET, STRAND 44 0BARLB8 OBIFrm <* OO.'S PUBLWATlOiTa. gBirnirs wautical series. Ninth Edition. Beviaed, with Chapters on Trim, Buoyancy, and Calcula- tions. Numerous lUmtrations, Handsome Cloth, Crown 8vo. Price 7s, $d. KNOW YOUR OWN SHIP. Bt THOMAS WALTON, Naval Arohitbct. Speoial/y arranged to suit the requirements of Ships' Officers, Shipowners, Superintendents, Draughtsmen, Engineers, and Others. This work explftlni, in a Bimple mAniMr, anoh Imjportant Bobjeota m:— DtoplMemMit.— Deadweight —TomwtO'—FnebMrd. — Moments.— Booy»iM7.~Stni]i.->8trDctiire.— Stob- Uity.— Boiling.— BallABting. — Loading.— Shifting Oargoee. — Admliilon of Water.— Ml Area-— Ac. "The little book wlU be foond ■xciidiiioz.t haitdt by meet oSeers and offldals connected with ahlpping. ... Mr. Walton's work will obtain uinrite avociaa, becanae of Ita onHoe fltneaa for thoae for whom It haa been wrl%\ea."~8hipsrtMg World. BY THM SAMB AUTHOR, Steel SUps: Tbeir Gonstmctioii and Maintenanee. (See page 38.) Sixteenth Edition, Tlyoroughly Rewired. Large %vo. Cloth, pp, i-xziy+712. With 2i50 lUustraHons, reduced Jrom Working Drawings, and 8 Plates. 2ls. net, A MANUAL OF MARINE ENGINEERING: OOMPRISmO THE DESIGNING, OONSTRUCTION, AND WORKING OF MARINE MACHINBRT. By A.E. SEATON, MJ.C.E., H.LHeGh.B., M.LN.A. General Contents. — Past I. — Prinoiples of Marine Propolaion. Pa&t IL — PrinoiDlee of Steam En^eenng. Part IIL — Details of Marine Engines : Design and Calcnlationa for Cylinders, Pistons, Valves, Expansion Valves, &c. Part IV. -- Propellers. Part V. — Boilers. Part VI. — Misoellaneous. "The Htadent, Draughtmian, and Ennneer will find this work the Hoei taloablb Haicdbook ot ReiarBnoe on the Marine Engine now in existenoe."— Jforfne Emtftmsr. Ninth Edition, Thoroaghly Revised. Pooket-Sise, Leather. 8s. 6d. A POOBXT-BOOK OF HilRIN£ ENGINEERING RULES AND TABLES, TOR THE VSS OF Marine Bnglneex^ Naval Arehlteets, Deslniers, Draugrhumeii. Saperintendents and Otnen. Bt a. K 8BAT0N, M.I.O.E., M.I.M6oh.K, M.I.N.A.: AND H. M. R0UNTHV7AITE, M.LMech.E., M.I.N.A " The best book of ita Und, and the information la both ap-to-date and reliable."— Sngineer. lONOON: CHARLES GRIFFIN * CO.. UNITED, EXETER STREET. STRAND. aNQlJtrSBRlNB AND MSOHANIOS. 45 WORKS BT PROF. ROBERT H. SMITH, A8Soe.M.I.C.B.t lLllfeota.&, ILLCLS., ULliiiiX, Wblt Soli., M.0r4.KeiJL THE CALCULUS FOR ENGINEERS AND PHYSICISTS, Applied to Teehnical Problems. WXTB ULTJUHHIVJI OI1A88IFIBD BEFEBBHOH IiIST OF INTBGRAI18. By PROF. ROBERT H. SMITH. A88ISTBD BT a F. MT7IRHEAD, M.A., B.Sa, Vonnerljr OI«k Ftllow of GkHfow UniTvnity, and Leotarw on MatbeinAtlai *t MMon Collage. In Cnnwn 8vo, txtra^ toKA DuigrafM and Folding'PlaU* 8b. 6d. ** PxoF. &. H. Bwrntt book wiU be wrrloeabte In rendertng e bexd roed am iabt ai riAOTio ▲BU for the DOQHnetheiiietleel Skadont and Bngtaieer.''— ^ItikaMniei. '* IiihiiirtlnijIliiiieiiM. wtth piseUeel iUnatrettona of aotnel ooenneiio^ ere to be foond bMe iB eboBdanoe. Thb tut oomplitb CLAsainiD msriBBVCB tablb will prove veiy metal tai leTliif the time of thoee who went en intesrel In e lNiR7.''~Tk« Rngkmr, MEASUREMENT CONVERSIONS (Bnglish and French): 43 GRAPHIC TABLES OR DIAGRAMS, ON 28 PLATES. Showing At » glanoe the Mutual Ck)KVEB8iON of Mxasubbmxhtb in DmiBiMT Units Of XiOngUui, Areas, Yolomei, Welghte, Streseei, Densitlee, QoantttlsB of Work, Bone Powers, Temperatures, *e. fw t*e aw# of Eagiumn, SunMifon, AnkHaaU, whI Oattnatott, In 4tOf BoitniB, 7s. 6d. * * Prof. Smith's OomriBSiON-TABLBB form the meet nnione end oom- prehensiYe ooUeotion ever placed before the profesrion. By their nse mveh lime and labour will be saved, and the chanoes of error in oalonlation diminished. It Is believed that henceforth no Engineer's OflSoe wOl be oonsidered complete without them. Pocket SlMtLaetlier Limp, with OUt Bdgee udA Bounded Comen, printed on SpeeUl Thin Peper, with XUnetratlonB, pp. 1-xU + 8S4. Price 1&. net. (THE NEW "NYSTROM") THE MECHANICAL ENCIHEER'S REFERENCE BOOK A Handbook 0/ Taibiea^ FormuloR and Methods for Engineers, StvdmU and Draughtsmen, By henry HARRISON 8UPLEE, B.Sc., M.E. *' We feel sure it will be of great eenioe to mechanical vn^9«n.'*'-'Rnginttring. LONOON : CHARLES GRIFFIN A CO., UMITEO. EXETER STREET. STRANa 46 0HARLB8 9RIFFi2i S 00.'8 PUBLIC ATIOJS 8. Smohd Editiov. In Luge 8vo. Haadaome Cloth. 168. CHEMISTRY FOR ENGINEERS. BERTRAM BLOUNT, aitd A. O. BLOXAM, FXa, F.Ofl^ A.IO.B. F.La, F.oa OUBHBBAL GOUTBHn.— Ibtrodaotton— COMmiitry of tho Obicf Katoilftli of OoBstmoUoii— Sonrooi of Baorgy— cmomlslry of Btoun-nlitDg— Ohtals- try of lAlxrloKtlmi and lAtnlMuito— Hotallnrglma Proowioi iimA I& tto WlBBlBf aad Maimftwtttro of Metali. **The antlion haTe ■uogudbd beyond all expaetetton, and luTe prodnoed a inxk which ■honld gtvs VBMS PowsB to the £niiliiMr and Jfennftotiirer/'— fTfc« I^bmi. By the same Authors, " CmaasTRT for MAKUFAcrnmxBS," seo p. ?!• THE ELEMENTS OF CHEMICAL ENGINEERING. By J. GS088MAKN, M.A., Ph.D., P.I.G. With a Preface by Sir WiLUAM Rahsat, K.G.B., F.R.S. In Handaome Cloth. With nearly 60 BlnatrationB. Se. 6d. net [See page 70. In Demy Quarto. With Diasrams and Worked ProUema. 2b. 6£ net. PROPORTIONAL SET SQUARES APPLIED TO GEOMETRICAL PROBLEMS. Bt Lisut.-Col. THOMAS ENGLISH, Late Royal Engineers. Works by WALTER R, BROWNE, M.A., M.InslCE. THE STUDENT'S MECHANICS: An Introdnetioii to the Study of Foree and Motion. Wi& Diagimma. Crown Sto. Cloth, 4s. 6d. "dear hi ttyle and pmcdcal in okethod, 'Tmb Sroowarft UmaujKia* ii oovdklly lo be reoomoMBded from all poiuu of new. **— >l tMttuntm. FOUNDATIONS OF MECHANIC^ PapeiB reprinted from the En^nur, In Crown 8to, is. Demy 8to, with Numerous Illustrations, 98. FUEL AND WATER: A Manual for Users of Steam and Water. By Pbof. FRANZ SCHWACKHOFER op Vibnna, and WALTER R. BROWNE, M.A., CE. * OmNBBAL Com awii.— Heat and Combustioii— Fuel, VarietiM ol^Firiiiff Amasa FWnaoe, FhML ChimiMy— Tho Boiler, Choice of— Vari«tiea^rfled*wat« aei Steam Pipee Water; CompoeitioD, ParifioRtion— Prevenlioa of Scale, &c, ftc "Ibe Sectioa on Heat it one of the best and moet lucid e?er wiitten.''—iriyiwi»r. UWOON: CHARLES 8RIFFIN ft CO., LIMITED, EXETER STREET, STRANa OHARLSa OBIFFIN A OO.'S PUBUCAT10N8. 47 CHIFFIH'8 LOCAL COYEBMMEMT HANDBOOKS. W«RK3 SIOTABLS 70& ICUKICOtPAL AND COUNTY BNGINBBBS. ANALYSTS, AND 0THSB8. See alBo DaTles' BygitM^ p. 99, and MacLeod's Cdtetilatiotu, p. 110 General Catalogue. Oas Manufaeture (The Chemistry of)- A Handbook oq the Pro- dnetion, PorifleatioD, and TeiUng of DluminatlDg Oaa^and the Avay of Bjre-Pro- dncta. £7 W. J. A. BumRriBLD, M.A., F.LCm.V.C.S. With Illoatrationa. FOUBTH BDRlOHiBeYlMd. Vol. L, 7i. 6d. net. Yol. U., in preparation, (See page 77. Water Supply : A Practical Treatise on the Selection of Sonroea and the DIttrlbation of Water. By Kegisald B. Middlbton, M.Inst.G.B., H.Inst.Mech.S., F.S.I. With Nnmeroni Plates and Diagrams. Crown 8to. 8s. 6d. net. [See page 77. Central Eleetrieal Stations : Their Desisn, Orfinniaation, and Manage- ment ByC. H. WOBDINQHAM, A.K.C., ILLCB. SboordBditigh. Ste. net. [Seep. 48. Electricity ControL By Leonabd Andrews, A.M.In8t.C.£M M.I.E.B. 12s. 6d. net. [See page 48. Electricity Meters. By Henby G. Solomon, A.M.In8t.E.E. 16e. net. [See page 49. Trades* Waste : Ita Treatment and Utilisation, with Special Reference to the Prevention of Kiyers' Pollution. By W. Natlor, 7.C.8., A.M.Inst.C.B. With Numerous Plates, Diagrams, and Illustrations. 21s. net. [See page 76. CalcareoOB Cements : Their Nature, Preparation, and Uses. With some BemarkB upon Cement Testing. By OmmtT Bidoratb, AaBoo.Inst.C.B., and Chas. Spaokxan, F.C.8. With ulustratloos, Analytical Data, and Appendices on Costs, Ac. 16s. net [See page 76. Road Making and Maintenance : A Practical Treatise for Engineers, Smnreyors, and others. With an Historical Sketch of Ancient and Modem rraotloe. aTHOXAS AmuN, Asaoc.M.Inst.C.B., M. Assoc. Municipal and County Bngrs.; San. Inst. Sboohd Bdition, Bevised. Fully Illustrated. [See page 79. Light Railways at Home and Abroad. By William Henbt Colm, M.Inst.C.B., late Deputy Manager, North-Westem railway, India. Large 8to, Handsome Cloth, Plates and Illustrations. 16s. [See psge M. Praetieal Sanitation : A Handbook for Sanitary Inspectors and others Interested in Sanitation. By Oio. Bud, M.D., D.P.H., Medical Officer, Staifordshlre County CouncU. With Appendix (re-written) on Sanitary Law, by Herbert Manley, M.A., M.B., D.P.fl., Barrister-at-iAW. Thibteihth Bdrioh, Thorou^y Bevlaed. 6s. [See page 78. Sanitary Engineering: A Practical Manual of Town Drainage and Sewage and Befuse Disposal. By FaANOis Wood, A.M.Iust.C.B., F.O.S. Siooir]> BDinoii, Bevlsed. Fulliy Illustrated. 8s. 6d. net. [See page 78. Dairy Chemistry: A Practical Handbook for Dairy Managers, Chemists, and Analysts, fiy H. Dboop Biohicohd, F.I.C., Chemist to the Aylesbury Dairy Company. With Tables, niustratlons, 4%. Handsome Cloth, 16s. [See page 78. Dairy Analysis : The Laboratory Book of. By H. Dboop Richmond, F.I.C. Fully Illustrated, Cloth. 2s. 6d. net. [See page 78. Milk: Its Production and Uses. With Chapters on Dairy Farming, The Diseases of Cattle, and on the Hygiene and Control of Supplies. By Bdwasd F. WiLLOVeBBT, M.D. (Lond.X D.P.H. (Lond. and Camb.), Os. net [See page 78. Flesh Foods: With Methods for their Chemical, Microscopical, and Bacteriological Bzamination. A Handbook for Medical Men, Inspectors, Analysts, and others. By C. Aihsworth Mitohxll, B.A., F.LC, Mem. Council Boc of Pnblio Analysts. With numerous Illustrations and a coloured Plate. 10B.6d. (See page 7^ Foods: Their Composition and Analysis. By A. Wyntxb Bltv M.B.C.8., F.C.S., Public Analyst for the County of Devon, and M. W Alti B.A., B.8o. With Tables, Folding Plate, and Frontispiece. FmH BDmo Thoroughly BcTlsed. 21s. [See page t LONDON : CHARLES ORIFFIN « CO.. LIMITED. EXETER STREET. STRANa 48 OBABLta QRIFWIS 4 .'8 PUBMOATlONa. ELECTRICAL ENGINEERING. Second Edition, Revised, in Large 8cv. ffandsomt Cloth, Fnfmefy lUusinUed wUh Platet^ Diagrams^ and Fig$irts. 2^» met* CENTRAL ELECTRICAL STATIONS: Their Design, Orffanisation, and Hanasrement. ByCHAS. H. WORDINGHAM, A.K.C.»M.Inst.CE.,M.Inst.Mbch.E., Late Memb. of Council InstE.E., and Electrical Cngineer to the City of Maadiester ; Electrical Engineer-in-Chief to the Admiralty. ABRIDaSD OONTSNTS. Introductory. — Central Station Work as a Profession. — As an Investment.— The Sstab* lishment of a Central Sution —Systems of Supply.— Site.— Arehitecturt.— Plant.— BoBen ^> Srsteras of Drau^t aiMl Waste Heat Economy.— Coal Handling. Wei^uag, and Stosiag.- Tne Transmission of Steam. — Generators. — Condensing A^ianoes. — Switching Gear« Instruments, and Connections. — Distributing Mains.^lnsuIation, Resistance, and Coat— ^ Distributing Networks — Senrice Mains and Feeders. — Testinar Mains. -^Meten and Appliances. — Standardising and Testing Lab<»atory.^Secondanr Battcries.-^treel li^ht* iag. — Cost — General Organisation —Mains Deportment — Installation Department — Standardising Department — Drawing Office — Qerical Department- The Consumer.— Rontine and Main Xaying'—lNDBX. " One of the most valuablk contkibutioms to Central Station literature we have had for some tbnt."—£Uciriciiy, In Large 8vo. Handsome Cloth. Profusely lUttstiated. las. 6d. net. ELECTRICITY CONTROL. A Treatise on Kleetrte Swltebgear and Sjrstems of Bleetrle IttmsmlMlon. By LEONARD ANDREWS, Associate Membei of the Institution of Civil Engineers, Member of the Institution of Electrical Engineers, &c General Principles of Switchgear Design.— Constructional Details — Orcuit Breakers or Arc Interrupting Devices.— Automatically Operated Circuit- Breakers. —Alternating Reverac Current Devices. —Arrangement of 'Bus Bars, and Apparatus for Parallel Running.—' General Amnnment of Controlling Apparatus for High Tension Systems. — General Arrangement of Controlling Apparatus for Low Tension Systems.— ^Examples of Complete Ias«aljations.->Long Distance Tmnamission Schemes. *' Not often does the specialist have presented to him so satisfactory a book as this. . . . We recommend it without hesitation to Central Station Engineers,- and, in &ct, to aayona interested in the subject" — Pvwtr, Eighteenth Edition. Leather, Pocket Siae. Ss. 6d. A POCKET-BOOK ELECTRICAL RULES & TABLES FOR THE USE OF ELSCTRICtANS AND ENGiNEERS, By JOHN MUNRO, C.E., ft Prof. JAMIESON, li€.lNST.C.E., F.R.S.& aXKHBAL OOKTSHTS. Units of Measurement -- Measures. — Testing. <- Conductors. — IKelectrics. — Subaaarine Cables.— Telegraphy.—Electro-Chemistiy.—Electro-Metallurgy.—Battcaries.— Dynamos and Motors.— Trans(wmers.-^£lectric Lighting.— >Miscel]aneous.--Logarithms.— Appendices. " WoirxAXFULLT PnvicT. . . . Worthy of the highest commimdation we can five \tJ*—EUetrieum, lONOON : CHARLES GRIFFIM « CO, UNITED. EXEHR STREET. STRANa BLSCTRICAL ENQINEBBINO. 49 In Large 8vo. Profusely Illustrated. 8a. 6d. net. WIRELESS TELEGRAPHY. By GUSTAVE EICHHORN, Ph.D. Contents.— OscillationB.— Closed Oscillation Systems.— Open Oscillation Sjvstems. — Coupled Systems.— The Coupling Compensating the Aerial Wire.— Tne Receiver. — Comparative Measurement m the Sender. — Theoretical Results and Calculations in respect of Sender and Receiver.— Closely*Coupled Sender and Receiver.— Loose-Coupled Sender and Receiver.— Principal Formula.— The Ondameter. — Working a Wireless Telegraph Station. — Modem Apparatus and Methods of Working.— Conclusion.— Bibliography. — ^Indez. "Well written . . . and comblneB with a good deal of deicription a careful inveitigation of tiie fondamental theoretical phenomeua."— iTofure. Large 8vo, Handsome Cloth, with 3H4 Pages and 307 Illustrations. 16s. net. ELECTRICITY METERS, Bt henry G. SOLOMON, A.M.Inst.E.E. C0MTSMI8.— Introductory. •* General Principles of Continuous -Current Meters. — Continuous-Cunent Quantity Meters.— Continuous-Energy Motor Meters.— Different Types.— Speoal Purposes, i«.. Battery Meters, Switchboard Meters, Tramcar Meters.— General Principles of Single- and Polyphase Induc- tion Meters.— Single -phase Induction Meters. — Polyphase Meters. — Tariff Systems. — ^Prepayment Meters. — ^Taiiff and Hour Meters.— Some Mechanical Features in Meter Design.— Testing Meters.— Index. " An eameit and sncoesafnl attempt to deal oomprehenaively with modem methods of meaearinK current or power in electrioal iiutallationB.**— JTM^MMertfn^. '' Trustworthy information. . . . We can confldently recommend the book to every eleotrical engineer." - £l§eirieUif. Second Edition, Cloth, Ss. 6d. Leather, for the Pocket, 8s. 6d. OBIFFIN'S BLEOT&IOAL PBIOB-BOOK : For Electrical, Civil, Marine, and Borough En^eers, Local Authorities, Architects, Railway Contractors, &c., ftc. Edited by H. J. Dowsing. '* The SLBcraicAL PaicB-Booit asMovn axx mvstbkv about the eoet of Slectrkal Power. By Ite aid Ae axntiisB that will be entailed by utUisiag electrictcy ea a kfge or imall esale can be diecovered.**— ^frA«<«r<. ELECTRIC SMELTING AMD REFINING. By Dr. W. Borchibs and W. 0. McMillan. Sboono Edition, Revised and Enlarged. 2 Is. net. [See page 67. ELECTRO • METALLURGY, A Treatise on. By Walter O. McMillan, F.I.G., F.C.S. Second Edition, Reyised and in Part Re- Written. 10s. 6d. [Bee page 67. ELECTRICAL PRACTICE IN COLLIERIES. By D. Burns, M.E., M.Inst.M.E. 8R00ND Edition, Reyised and greatly Enlarged. 7s. 6d. net. [See page 66. LONDON: CHARLES 8RIFFIN « CO.. LIMITED. EXETER STREET, STRAND. 50 CBARLB8 QRIPFIN A OO.'S PUBLIOATIONB. By PB0FES80B8 J. H. POYNTINO k J, J. THOMBOM. In Five VolamM. Lftrge Sro. Bold Sepfttately. A TEXT-BOOK OF PHYSICS. J. H. POTNTING, J. J. THOMSON. iMtoJUlowof TMalt7 0oU«n,aunbridc«: Sallow of Trtnltj OoUaiek OtmMdift: PtoL PNienor of Fliyiloi, wulngham ofSiptrtiiiantelPliTttailiitbaUBmrrilr UnlTonitj* of OftmbrkUt. iHTRODnoTOBT VoLUMB. FoxTBTH EDITION, ReviBed. Fully Bliifinted. 10b. 6d. OoBTBRS. — QnTltetloTi. — The Aoeetoratton of Qmvtty. — KtoaUdftr.— BttMiM and BtniiiA.*Tonion.— B«ndlaff of £od8.~Sptr»l firings. «»OolltoloBu-»Oocapt. OomnBTB.— The Nature of Sonnd and ita ohief Oharaeterlstioa— The /eloelty of Boond in Air and other M«dia.^ReflecTlie TraasTBBBB VIbrationa of Stretobed Stringa or Wires.— Plpea and other Air Gavltlea.— BodB.— PIbBbbl —Membranea.— Vibrations maintained by Heat^SensitiTe Flames and Jeta.— MnalflBl Sand.— The Soperpoaltion of WaToa.— Ibdrx. " Tliework . . . maybe recommended to anyone deainms of possHssing an babt DP^o-DATB 8Tijn>ABi> TmBJLTiSB on Aoousttos.*'— Itfterolafs. '* Very clearly written. . . . The names of the anthors are a fnaiaatee of ihm scBmavLTio aoouxaot and up-to oats OBAXAorn of the work.**— ir^iMeaKoNsJ TUma. VoLUMa ni. Secokd Edition, ReviBod. Folly IlluBtrated. Price IGs, HEAT. COHTBWW. —Temperature. — Kxpansion of SoUda.— LiqnidB.— Oasea.— drenlatlon and GonTeoUoD.— 4)iiBntity of Heat; Speolflc Heat.— GondnctlTlty.—FonnB of Bneiiy; ConserTBtlon ; Meohanical EqniTalent of Heat.— The Kinetio Theory.— Cbange of State; liquid Vapour.— Critical Points.— Solids and LiqaldB.- Atmospheric Conditions. — Badlation. —Theory of Exchanges.- Badiation and Temperatnre.— niennodynainloB.-^ Isothermal and Adiahatic Changes.— Thermodynamics of Changes of State, and Soln- tlons.— Thermodynamics of Badiation.— Indbz. I" Well ap*to^te, and extremely clear and exact throoghont. ... As clear bb it would be possible to make such a text-book.' —.ATcUiifv. Remaining YolnmeB in Preparatiqn — LIQHT; MAGNETISM AND ELECTBICITY. THE MEAN DENSITY OF THE EARTH : An Eeaay to which th« Adams Prise was adjudged in 1898 in the Uniyeisity of Cambridge. By J. R. PoTVTnre, 8e.D.. F.B.8., Late Fellow of Trinity College. OambridoB: Profeaaor of Physics, Birmingham UmTersity. In Large Sro^ with Bibliography, IlIustrBttans tn the Text, and Seven Lithographed Plates. 12s. 0d. "Cannotfall to be of orbat and qinxkal ivrribt.''- ^tAeiuBum. LONDON : CHARLES GRIFFIN A CO., LIMITED. EXETER STREET, STRAND. Griffin's Goologiool, Prospootlnft Mining, and Metallurgloal Publloatlons. G6ology, Stratigraphical, t, Praetieal Aids, . M Open Air Studies, . Mining Geology, . Prospeeting for Minerals, Food Supply, . Ore and Stone Mining, . Elements of Mining, E. Ethuudok, F.R.S., . Pbof. Gbknyillb Oolb, f> II James Pabk, F.Q.S., . S. HSRBBBT Ooz, A.R.S.M., RoBT. Bbuce, Sib 0. Lb Nb7b Fostbb, Coal Minin Practical C Elementary II 91 Coal Mining, H. W. Hughes, F.O.S., G. L. Kbrb, M.InBt.M.£., Elect. Colliery Practice, Mine-Sunreving, Mine Air, Investigation of, Fosteb and Haldanb, Mining LaW, G. J. Alfobd, Blasting and Explosives, 0. Guitmann, A.M.I.O.E., Testing Explosives, . Bichel akd Labsbn, . Shaft Sinking, ... J. Ribmbb, . Mine Accounts, . Pbov. J. G. Lawk, Mining Engineers' Pkt«-Bk., E. R. Fibld, M.Inst.M.M., Petroleum, .... Sib Boyertok Redwood, A Handbook on Petroleum, Thomsoh akd Redwood, OU Fuel, . Mineral Oil Testing, . Metallurgical Analysis, . Microscopic Analysis, Metallurgy (General), „ (Elementary), GettinfiT Gold, . Cyanide Process, . Cyaniding, Electric Smelting, . Electro-Metallurgy, Assaying, Metallurgical Analysis, PAOX 52 62 85 56 53 53 54 54 55 55 „ „ 55 D. BuBKS, .... 56 Bekkstt H. Bbough, A.R.S.M., 56 54 57 58 58 58 57 57 61 61 61 61 60 SiDKET H. North, J. Hicks, Maoleod akd Walxeb, F. OsMOKD & J. E. Stead, F.R.S., 60 Phillips akd Baubbmak, Pbov. Humboldt Seztok, J. C. F. JoHKsoK, F.G.S., Jahes Pabk, F.G.S., . JULIAK AKD SmABT, BOBOHEBS AKD M^MlLLAK, W. G. M^'MlLLAK, P.I.C., J. J. A 0. Berikgsb, . J. J. MOBOAK, F.C.S., 60 66 59 59 59 67 67 66 66 Metalluigy (Introduction to), Sib W. Robbbts-austek, K.O.B., 63 Gold, Metallurgy of. Lead and Silver, „ Iron, Metallurgy of. Steel, „ General Foundry Practice, Iron-Founding, . Precious Stones, Db. Kibke Rose, A.R.S.M., 63 H. F. OoLLiKS, A.RS.M., . 64 Thos. Tubkbb, A.R.S.M., . 65 F.W.Habbobd, ... 65 M^'WlLLIAM AND LoKGMUIB, 68 Pbov. Tubkbb, ... 68 Db. Max Baueb, 68 LONDON : CHARLES 8RIFFIN « CO., LIMITED, EXETER STREET, STRAND. 52 CHARLS8 GRIFFIN df €0:8 PUBLICATIONS. Demy Svo, Handsome oloth, 348* Stratigrapbical Geology & Paleontology, OJi TEE BASIS OP PHILLIPS. By ROBERT ETHERIDGE, F.R.S, OfT TMB NATVILAI, MIST. DBPARTMBirr, BRITISH MVSBUM. LATB PAUHONTOLOdST TO TMB CBOLOGICAL SVRVXY OF CRBAT BJUTAIN. PAST PRBSIDENT Of THS GBOLOGICAL SOCIBTY. BTC TRAftb Aap, numerous arables, and Hbfits^dix platctf. '* No sodi conpa&diiun of f eologiod knoirlisdce hot ever been bnra^t together before. "— WTtstmimter Xevitw, II If Pkop. Sbblst's volume was reauiicBble for its origimttty Bad the hraeddiflf its Mr. Ethbbidgb fuUr justifies the assertion mede in his pre&oe that his book diSen im gtnictioB and detail from any known manual . . . Must take high bahx ahoho OP BBFBKBMCB. *—■<< tk§tuntm. AIDS IN PRACTICAL GEOLOGY; WITH A SECT/ON ON PALj^ONTOLOGV. By professor GRENVILLE COLE, M.R.I.A., F.G.S. Fifth Edition, Thoroughly Revised. With Frontispiece and Illustrations. Cloth. los. 6d. aBNXRAL OONTIINTB.^ PART I.— Sakpuno of the Earth's Crust. PART II.— Examination of Minx&als. PART III.— Examination of Rocks. PART rv.— Examination of Fossils. "Dbsbbving OP THB HIGHEST PBAts*. Here indeed ens 'Aids* imruiuatABLB sod IMVALUABLB. All the directions are given with the utmost dearoess and psecision.* — "Tluit the work deserres iu title, that it is full of 'Aids/ and in the bichft 'pBAcncAL,' will be the verdict of all who use it"— JVJ»/wfif. An Introduction to Qeolosy Out-of-doors. By PROFESSOR GRENVILLE COLE, M.R.I.A., F.G.S. For details, see Griffin's Introductory Science Series, p. 85. Crown 8zv. Handsome Cloth, 2s, 6d, RESEARCHES ON THE PAST AND PRESENT HISTORY OF THE EARTH'S ATMOSPHERE. Including the latest DIsooueries and their Pmotioal Applioations, By DR. THOMAS LAMB PHIPSON. Part L — ^The Earth's Atmosphere in Remote Geological Periods. Part II. — The Atmosphere of onr present period. Appendices ; Index. " The book should prove of interest to genera] readers, as well as to meteorologists and other students of science." — Naiurt. U)NDON: CHARLES GRIFFIN I CO.. UUlTEO, EXETER STREET, STRAW). PROaPKOTING AND COLOmaATION. 53 GBIFFIN'S "WEV LABTD" SEBIES. Practieal ffcmd-Books /or the Use of Fraapeetors^ Explorwa^ SeUUrSj Colonists, and all Interested in the opening up and Development of New Lands, EDCcm) BT GRENVILLE A. J. GOLE» M.R.I.A., F.O.a, Profenor of Oeologj in the Boyftl Collm of Soienoe for Ireland, and Jfizaminer In the Uniyenlty of London. In Orovm 8vo. HaaidBome Cleth, bs. With NwnerauB Maps SpeciaUy Drawn and Executed for this Work, NEW LANDS: THXIB BESOUBOES AlTD PBOSPECTIVB ADVANTAGES. By HUGH ROBERT MILL, D.So., LL.D., F.B.S.R, '*A mat Adminbly aiipplled. . . . Am the Advantage of helng written by a pro- fetaed QeogTapher.**-><9'eo9raj>Miea/ Journal. With many EngravingB and Photographa. HuidBome Cloth, 4s. 6d. FOOD SXJPPIjY. By ROBERT BRUOE, Agrieoltaral 8ap«lotMMkBt to the Koyal DaMin Sodety. With Appendix on PreMrred Fooda by C. A« Mxtchxll, B.A, F.LC. " The woric ii one which wtU appeal to thoae intending to beoome ftomen at homa or in the Ooloniea, and who desire to obtahi a fenaral iaea of the tme prtndplea vf fanning in all m tmAmoiae."^^cmnud qf tkt Royml OUcnial I§uL FouBTH Edition, Sevised. WUh IlUutrationB, ffamdsome Oloih, 6s, PROSPECTING FOR MINERALS. 4 Praotiea/ Handbook for Prospeotors, Explorers, Settlers, and all Interested In the Opening up and Deuelopment of Mew Lands, Bt 8. HERBERT COX, A8800.R.S.M., M.In8t.M.M., F.G.S., Profesaor of Mining at the Boyal School of Mines. GXNBRAL CoirTSNTB.~Introdnction and Hints on Geology— The Determin*- tion of Minerals : Use of the Blow-pipe, fta— Rock-forming Minenls and Kon* MMaUio IGnerals of Commercial Yalne : Rock Salt, Borw^ Marbles, litho- mphic Stone, Qnartz and Opal^ Ac., ftc.— Predons Stones and Gems— StraiLBed Deposits: Coal and Ores— umeral Veins and Lodes— Irrsgular Deposits- Dynamics of Lodes: Faults, Ac — ^Allnrial Deposits— Noble Metals: Grold, Pfatinnm. Silver, Ac— Lesa — Mercury— Copper— Tin — ZSnc— Iron — Nickel, Ac— Sulfur, Antimony, Arsenic, Ac — Combustible Minerals— Petroleun— General Hints on Piospectiag— Glossary— Index. " This ADKXRABLl LIXTUi WORK . . . written with BODDITinO AOOVKA07 in S ouum and lucid style. ... An iMPORTAire AnnmoH to technical Uteratuie . . . ^Mining JoumaL lONDON: CHARLES 8RIFFIN ft C0„ LIMITED. EXETER STREET, STRAND 54 0HARLE8 GRIFFIN A 00^8 PUBLIOATIONS. SIB CLEMENT LE NEVE FOSTER, D.Se., F.R.S. Sixth Edition. With Frontispiece and 716 Illustrations. Price 34b. ORE & STONE MINING By Sir C. LE NEVE FOSTER, D.Sc., F.R.S., LATB PROVBJiSOK OP MINIKG. ROYAL COLX.BCB OF SCIBMCB. Revised, and brought up-to-date By BENNETT H. BROUGH, F.CS., Assoc.R.S.M. GENERAL CONTENTS. INTRODUCTION. Mode of Oeemrenee of Minerals.— PpofpeeUnjr.—Bopliis. ^Breakinff GpoiumL— SapporUng Excavations.— Exploitation.— flanlajre or Transport.— Hoisting or winding. — Drainage. — Ventilation. — Ughtfng.— Deseent and Aseent.— Dresslng^Prlnclples oiBmplosrment of Mining Laboop. —Legislation affecting Mines and Quarries. — Condition of the Mlner.^ Aeddents.— Index. " We have Mldom had the pleasure to review a work so thorough and complete aa tile preseat one. Both in manner and in matter it i> FAR SUPsriok To AHTTHIHO 09 IXB SPKdAL SUBJECT HITHKRTO PUBLISHED IK ENOLAITD.'*— ^tAtflueum. " Not only 1b thla work the acknowledged text-book on metal mining in Great Britain and the Colonies, but that it is so regarded in the United States of America is evidenced by the fact that it is the book on that subject recommended to the studmts In most of the mining schools of that country."— TA« Time%, In Crown 8vo. Handsome Cloth. With nearly 900 Illustratioas, many of them being f nil page reprodactions of views of great interest. Price 7s. 6d. net. THE ELEMENTS OF MINING AND QUARRYING. An Introductory Text-Book for Mining Students. By Sir C. LE NEVE FOSTER, D.Sc, F.RS., ProfesBor of Mining at the Royal College of Science, London, with which is Incorporated the Royal School of Mines ; lately one of H.M. IiMpectors of Mines. Genkral Contentb. — Intboduotion. — Occurrence of Minerals. — - Pn>- specting. — Boring.— Breaking Ground.— Supporting Excavations. — Exploita- tion. — Haulage or Transport. — Hoisting or Wmding.— Drainage. — Ventilation. — Lighting. — Descent and Ascent. — ^Dressing, &c. — Index. ** A remarkably clear survey of the whole field of mining operations.**— Jffi{K*M^' " Barely does it fall to the lot of a reviewer to have to accord such unqualified praise aa this book deserves. . . . The profession generally have every reason to be grateful lo Sir C. Le Neve Foster for having enriched educational literature with so admirable aa elementary Text-book."— If imvy Journal. In Large Crown 8vo. Fully Illustrated. 6s. net. THE INVESTIGATION OF MINE AIR: An Account by Several Authors of the Nature, Significance^ and Practical Methods of Measurement of the Impurities met with in the Air of Collieries and Metalliferous Mines* edited by Sir CLEMENT LE NEVE FOSTER, D.Sc, F.R.S., And J. S. HALDANE, M.D., F.R.S. " We know of nothing essential that has been omitted. The book is liberally supplied with illustrations of apparatus." — CaUirry Guardian. LONDON : CHARLES GRIFFIN ft CO.. LIMITED. EXETER STREET, STRANK W0RK8 ON MINING. 55 WORKS ON COAL«MINING. Fifth Edition, Revised and Greatly Enlarged. With 4 Plates and 690 Illastrations. Price 248. net. A TEXT-BOOK OF COAL-MINING : FOR THE USE OF COLLIERY MANAGERS AMD OTHERS ENQAQED IN COAL-MIMINQ. By HERBERT WILLIAM HUGHES. P.G.S., Amoc. Royal School of Klnea, General Manager of Band well Park OoUiery. Gkneeal Contents. — Geology.— Search for Coal.— Breaking Ground. — Sinking.— Preliminary Operations. — Methods of Working. — Haulage. — Winding. —Pumpine.— Ventilation.— Lighting.— Works at Surface. —Pre- paration of Coal lor Market.— Indsx. *' Qalte TBI BUT BOOK of ItB kind . . . as pbactigal in aim as a book can be • . • The Ulustratlont are bxcbuuit."— ^tAaumn. '* We cordially recommend the work. "^CoOiery Chtardian^ ** Will soon come to be regarded as the stahdabd woek of its kind."-B{rmiii0Aam Dotty Ckmeitt, FoUBTH Edition, Thoroughly Revised and Greatly Enlarged. Re-set throughout. Liarge Crown 8yo. Handsome Cloth. 128. 6d PRACTICAL COAL-MINING': 4 MANUAL FOR MANAaiSRS, TTNDSR-MAKAailRS, OOLLIXRT UNaiMISERS, AND OTHORS. With Worked-out Problems on Haulagtf Pumping^ Fisn^t^tofi, dErc. By GEORGE L. KERR, M.E., M.Inst.M.E. Contents.- The Sources and Nature of Coal.— The Search for CoaL— Sinking.— Explosives.— Mechanical Wedges.— Rock Drills and Coal-cutting Machines.— Coal-cutting by Machinery.— Transmission of Power.— Modes of Workinjj.— Timbering Koadwavs.— Winding CoaL— Haulage.— Pumping. — Ventilation. — Safety Lamps. — Surface Arrangements, Surveying, Levelling, Ac. "An B9SB5TIALLT PBAOTiCAL woKK, and Can be confidently recommended. No department of Ooal-Ulning has been oTerlooked."— AiffdiMr*' CkiaeUt. In Crown 8vo. Handsome Cloth. With 200 Illustrations. 3s. 6d. ELEMENTARY COAL-MINING: FOR THE USE OF STX7DENTS, MINERS, AND OTHERS PREPARING FOR EXAMINATIONS. By GEORGE L.^KERR, M.E., M.In8T.M.E. Contents. — Sources and Nature of CoaL — Exploration and Borinjs for CoaL— Breaking Ground.— Explosives. Blasting, so. —Sinking and Fitting of Shafts. —Modes of Working. — Timbering Roadways. — Winding ana Drawing.— Haulage.— Pumping and Drainage.— Ventilation.— Cleaning and Sorting CoaL — Surveying, Ac. *' An abondanoe of information conreyed in a popular and attraeUre fonn. • • . Will be or great use to all who are in any way interested in eoal mining."— SeoCtM OriHc LONDON: CHARLES GRIFFIN « CO.. LIMITED. EXETER STREET. STRANt 3 56 OHARLES QRIFFIN A 00:8 PUBLICATIONS. Twelfth Edition* Revised. With Nameroiis Diagiams. Cloth, 7S. 6d. A TREATISE ON MINE-SURVEYINQ: For tke U9B of Managen of Minet and ColllerlM^ 8tudent8 at the Royal School of Minea, do. By BENNETT H. BROUGH, AssocR-S-M, F.G.S., Fonaerly Instnictor of Mine-Surveying, Rojral School of Mines. Contents. — General Explanations. — Measurement of Distances. — Miners Dial.— Variation of the Magnetic Needle.— Surveying with the Magnetic Needle in the Presence of Iron. — Surveying with the Fixed Needle. — ^The Go'man DinL— The Theodolite. — Traversing Undez^gfround.— Surface Survesrs with the Tbeodo- lite. — Plotting the Survey. — Calculation of Areas.— Levelling.— Connection of the Underground and Surface Surveys. — Measuring Distances bjr Telescope. — Setting- out.— ' Mine-Surveying Problems. — Mine Plans. — ^Application of tne Magnetic Needle in' Mining. — Photographic Survesrs. — ^Appendices. — Index. "Its CLBARJfSSS ofSTYUl. LUCIDmr of DBSCRimON, and FULNESS ofDBTAXL have lomr 0(0 WOK forttaoUoemiiqiM ia the Uteratoreof thJtbnmch of lafailiiff fwglweering. end the pteMiit eotiea Mb maintann the hl^ itandard of Itapredeceaaors. To the student, and to me mining engineer aUkc, ITS VALUB is inestimable. The fflustratlonaaM exoaUent."— 7*A« Mimnr y^unuO, Grown Svo. Haodaome Cloth. lUnstrated. 6e. MINING GEOLOGY. A TEXT-BOOK FOR MINIKa STUDENTS AMD MINEB8. By PROF. JAMES PARK, F.G.S., M.lDBt.M.M., f enor of Mining and Director of the OtMO Univenity School of Mines ; late Direetor Thames School of Mines, and Geological Surveyor and Mining Geologbt to the Government or Kew Zeeland GiHBRAL Ck>NTBiiTB.— Introduction.— ClassUlcatlon of Mineral Depotlta.— Ore Veins, their Filling, Age, and Structure.— The Djnamlcs uf Lodes and Bed8.~0re Depoeltt Oenetloally Considered— Ores and Minerals Considered Economically.— Mine Sampling and Ore Valuation.- The Szamlnation and Valuation of Mines.— Index. " A work which should find a place in the library of every mining engineer.*— Miining World. Second Edition. In Crown Svo, Handnome Ohth, WUh 30 New IlluMraiiona. la, 6d net, ELECTRICAL PRACTICE IN COLLIERIES. By D. burns, M.E., M.In8T.M.E., Oertlfloated Colliery Manager, and Lectorer on Mining and Geology to the Glasgow and Wart of Scotland Technical College. TTnite of Meaeorement, Condnotora, &c.— The Theory of the Dynamo.— The Dynamo, Details of Construotion and Working.— Motors.— Lightmg Installa* tions in Collieries. — Pumping by Electricity. — Electrical Haulage. — Coal Catting.— MiBceUaneoiis Applications of Electricity in Mines.— Coal Mines Hegulation Act (Electricity).— Indbx. "A dear' and oonoise introdnction to electrical praotioe In collieries."— JTiiidv -JoumoL LONDON: CHARLES QRIFFIN « CO., LIMITED. EXETER STREET, STRAND. WORKS ON MINING, 57 WORKS FOB MINEBS AND STUDENTS. In Crown 8vo» Handsome Cloth. 8b. 6d. net. MINING LAW OF THE BRITISH EMPIRE. £t CHARLES J. ALFORD, F.G.S., M.In8t.M.M. CoKTKNTs.— The Principles of Mining Law.— The Mining Law of Great Britain.— British India.— Ceylon.— Burma. — The Malay Penmsula. — British North Borneo.— Egypt. — Cyprus. — The Dominion of Canada. — British Oniana.— The Gold Coast Colony and Ashanti.— Cape of Grood Hope. — Natal. — Orange River Colon v. — Transvaal Colony. — Rhodesia. — The Commonwealth of Australia.— Kew Zealand, &o.— Indsx. ' Sbonld be specially useful to all those enga&ed in the direction of mining entitT- ptiaM.**— Financial I'imea, "Gsnnot fail to be useful . . . we cordially recommend the book."— Jfim'n^ ITorltf In Large Svo, Foukth Edition. Price lOi. fid. Mine Accounts and Mining Book-Keeping. Fop Stadents, Mana^eps, SeeretarieSt and others. With Cxampies taken from Actual PraoHoe of Leading Companies, Bt JAMBS GUNSON LAWN, A.R.aM., AM.Iiiat.C.B., F.0.&, Head of the Mining Department, Camborne School of Mines. Bditbd bt Sib 0. LB XBV£ F08TBR, D.8o.» F.KS. G0NTSNT8.— Introductioii.— Pabt L Enqaosmbnt and Patmbnt of Work- men.— Bngaffement of Workmen and Period between Pay Days. — Data determining Grofls Amount dne to Men.— Deductions. —Pay Sneeta. Due Bilk. —Pay Tickets. Part IL Pubohabrs and SALiB.^Puichase and Distribution of Stores.— Sales of Product . Part IIL Working Summaribs and Analtbis. — Summaries of Minerals Raised, Dressed, and Sold, and of Labour. — Analyses of Costs.— Accounts forwarded to Head Office. Part IV. Lxdokb, Balanox- Shxbt, and Comfant Books.— Head Office Books.— Redemption of GapitaL — Greneral Considerations and Companies Books. Part Y. Reports and Statistios. — Reports of Workings and Machinery of Mining Companies. — Mining Statistics.— Biblioorapht.— Index. **It leeoM Dfrounu to foggeet how Mr. Lawh*! book could be made more coMPun or andeznaiu more yaloabls, carefbl, and ezhaiiatlTe.*'— ilecotrntand* Magatim. Second Edition. In Pocket Size, Strongly Bound in Leather, 3s. 6d. Provided with Detachable Blank Pages for MS. THE MINING ENGINEERS' REPORT BOOK AND DIRECTORS' AND SHAREHOLDERS' GUIDE TO MINING REPORTS. By EDWIN R. FIELD, M.In8T.M.M. Witii Notes on tlie Valuation of Property^ and Tabulating Reports, Useful Tables, and Examples of Caloulatlons, do. "An ADiUBABLT oompUed book which Mining Bnglneers and Managers wfU find ■XXBBMELT UBBFUL."— JflffU'iy JowntoL LONDON: CHARLES GftlFFIN A CO.. LIMITED. EXETEB STREET, STRAND. 58 CHARLES GRIFFIN A CO:s PUBLIGATI0N8. "VOZtSS OXT tttXnLlSQt, aZPLOBXTAS, 8to. In Medium 8vo^ Handsome Cloth. With 18 Figures in the Text, and 19 Folding Plates. 10s. 6d. net. SHAFT-SINKING By J. RIEMER, Translated from the German J. W. B ROUGH, A.M.IN8T.C.E. Contents. — Shaft Sinking by Hand.— Shaft Sinking by Boring. — The Freezinfl; Method. — ^The Sinking Drum Process.— Biblioorapht.— -Index. "The translator deserves the thanks of the mining community for pladng this Tal liable work before them. . . . The work Is one which every mining engineer ■hoold include In his library."— Jftnin^ World. Second Bdition, Revised* In Large 8vo, with Numerous Illustrations and Folding P&tes. 10s. 6d. BLASTING: AND THE USE OF EXPLOSIVES. By OSOAR GUTTMA.NN, M.Inst.O.E., F.I.C., F.C.S. Contents. — Historical Sketch. — Blasting Materials. — Qualities and Handling of Explosives. — The Choice of Blasting Materials. — Preparation of Blsists. — Chamber Mines. — Charging of Boreholes. — Determination of Charge. — Blasting in Boreholes.— Firing.— Results of Working. — Variooa Blasting Operations. — Index. " Should prove a vade-mtcum to Mining Engineers and all engaged in practical work. •^Irtn and Coal Tradts Revirut. In Medium 8vo, Cloth. With many Illustrations in the Text. Four Full Page Plates and Four folding Tables.S^s. net. NEW METHODS OF TESTING EXPLOSIVES. By 0. E. BICHEL. Translated fbou the German and Edited By axel LARSEN, M.Inst.C.E, Contents. — Introductory. — Historical. — Testing Stations. — Pow«r Gauges. — Products of Combustion. — Rate of Detonation. — Length and Duration of Flame.— After- Flame Ratio. — ^Transmission of Explosion. — Conclusions. — Efficiency. "Its pages bristle with suggestions and actual experimental results to an extent seldom found In a rolume of five times its size."— uifTiw and Bxpiativet. LONDON: CHARLES fiRIFFIN A Ca. LIMITED. EXETER STREET. STRANft ~ MINING AND MBTALLUROT. 59 Sboond Edition, Revi&ed ThrougfunU, In Medium Svo. With Numerous Plates, Maps, and lUuatrationa. 21«. net, CYANIDING GOLD & SILVER ORES. A Practical Treatise on the Cyanide Process ; its Application, Methods of Worlcing, Design and Construction of Plant, and Costs. By H. FORBES JULIAN, Mining and Metallarglcal Engineer : Specialist in Gold : Late Teclinleal Adviaer of the Deatache Gold and Silber Scheide Anatalt, Fnuikfort-on-Malne. And EDGAR SMART, A.M.LaE., Oivil and Metallurgical Snglneer. " A handBome Toltune of 400 pages which will be a Talnable book of reference for all auociated with the proceas."— Jitnin^ Journal. "The authors are to be congratulated upon the production of what should proTe to be a standard woA.'*— Page's Magazine. In Large Crown %vo. With 13 Plates and many Illustrations in the Text. Bandsome Cfhth, Is. 6d. net. THE GTANIDE PROCESS OF GOLD EITRAGTIOM. A Text-Book for the Use of Metal/urgiete and Studenta at Sohoole of Mines, do. Bt JAMES PARK, F.G.S., M.In8T.M.M., Professor of ICining and Director of the Otago UnlTerslty School of Mines ; late DIreetor Thames School of Mines, and Geological Surveyor and Mining Geologist to the Goyemment of New Zealand. FouBTH English Edition. Thoroughly Reviaed and Greatly Enlarged. With additional details conoeming the Siemens-Halake and ouier recent prooeeees. •' Deserres to be ranked as amongst the BBT or rnxstnofQ TRaATiBH."— i/Mity Jaumel. Third Edition, Reviaed. With Plates and Illustrations. Cloth, 3a 6d. GETTING GOLD! A OOLD-MINING HANDBOOK FOR PRAGTIOAL MEN. By J. 0. F. JOHNSON, F.G.S., A.I.M.B., Life Member Australasian Mine-Managers* Association. GraaaAL Contents. —Introductory : Proepecting (Alluvial and General)— Lode or Beef Proapectins[ — Grenesiology of Gkud— Auriferous Lodes — ^Drifts- Gold Extraction— Liiiviation— Calcination— Motor Power and its Transmianon —Company Formation — ^i"i«g Appliances and Methods — Australasian Mhiing Regulations. "PaAoncAL from beginning to end . . . deals thoroughly with the Prospeoting, gtnking, Crushing, and Extraction of gold."— Bn'C. Atutralanan. In Crown Svo. Illustrated. Fancy Cloth Boards. 4«. 6d. GOLD SEEKING IN SOUTH AFRICA A Handbook of Hints for Intendinfir Explorers, Prospectors. and Settlers. By THBO KASSNER, Mine Muiscer, Author of the Qeoloffieal Sketch Map of the I>e Ksap Gold Fields. With a Chapter on the Agricultural Prospects of South Afrioa. ** As fascinating as anything erer penned by Jales Venie."— ij/Hean Commtru. lONDOM : CHARLES GRIFFIN ft CO., LIMITED. EXETER STREET. STRANH 6o CHARLB8 QRIFFIN A 00.*8 PUBU0ATI0N8. t - ■■ II ■ ■ Large 8vo. Handsome Cloth. With Illustratioae. 128. 6d. net. METALLUReiCAL ANALYSIS & ASSAYING : A THRBB YBAR8' COUR8B FOR STUDENTS OP SCHOOLS OF MINES. By W. a. MACLEOD, B.A., B.So., A.O.S.M. (N.Z.). Formerly AMlst-Direotor, Thames School of Minee (N.Z.), and Lecturer in Ohemiatry, Unitrenttjr of Tasmania : Director of Queensland Govemmeat School of Mines. Oharters Towers : And CHAS. WALKER, F.C.S., Lonstrator in Cbemlstry, Sydney UniTcrsit/ ; ] and HetaUorgy, Charters Towers School of Mines Part I. — Qaalitative Analysis and Preparation and Properties of Gases. Part II. — Qualitative and Qaantitative Analysis. Part III. — Assaying, Technical Analysis (Gas, Water, Fuels, Oils, &c. ). "The pabllcatioD of this volume tends to prove that the teaching of metalluigical snalyBlB and assaying in Anitralia rests in competent hands.**— iVaturf. Formerly Assist-Demonstrator in Chemistry, Sydney University ; Lecfeorer in Chemlstiy In Crown 8vo, Beautifully Illustrated with nearly 100 Microphotographs of Steel, &o. 7s. 6d. net. MIGROSGOPIG ANALYSIS OF METALS. By FLORIS OSMOND & J. E. STEAD, F.R.a, F.LO. CoNTKNTB. — Metallography considered as a method of Assay. — Ikfioro- graphic Analysis of durbon Steels. —Preparation of Specimens.— Polishing. —Constituents of Steel; Ferrite ; Cementite ; Pearlite; Sorbite; Martensite: Hardenite ; Troostite ; Austeoite. — Identification of Constituents.— Detailea Examination of Carbon Steels. — Conclusions, Theoretical and Practical — Apparatus employed. — Appbndtx. " There has been no work previously pabliahed in English calculated to be ao osefoi to the student in metallographlc research."— Iron and &Uel Tradti' Jtmmal. Third Edition. With Folding Plates and Many Illustrations. 368. A PRACTICAL TREATISE ON THE ART OF EXTRACTING METALS FROM THEIR ORES. By J. ARTHUR PHILLIPS, M.Inbt.O.E., F.C.S., P.G.S., dto. And H. BAUERMAN, V.P.G.S. Gxnkral Contents. — Refractory Materials. — Fire-Clays. — Fuels, &a — Alniniwinin. — Copper. — Tin. — Antimony. — Arsenic. — Zinc. — Mercury. — Bismuth. —Lead. —Iron. — Cobalt. —Nickel —Silver. — Gold. — Platinum. "Of the Third Edition, we are still able to say that, as a Text-book of Metallurgy, it jb the best with which we are acouainted.** — Mngineer. " A work which is equally valuable to the Student as a Text-book, and to the practical Smelter as a Standard Work of Reference. . . . The Ulustrafciaius are admirable examples of Wood Engraving.*' — Chemical Newt. LONDON: CHARLES GRIFFIN ft CO.. LIMITED, EXETER STREET. STRAND METALLURGICAL W0BK8, 6i 8100ND Edition, Revised, Enlarged^ and Re-aet Throughout on Larger Page* With ValuaJble Bibliography,' New Mapg^ lUustraiiona, dsc. 45«. net, A TREA TISE ON By sir BOVERTON RBDT^OOD, D.Sa, F.B.S.S., AwoclIkst.O.E., F.LO. Contents.— Section I.: Historical Account of the Petroleum Indaitry.— Seotion n.: GeolMical and Oeoeraphical Diatribation of Petroleum and Natural Gaa.— Seotion III.: The Chemical and FhyBical Properties of Petroleum and Natural Oas.-- Section IV.: The Origin of Petroleum and Natiual Oaa.— SECnoN V.: The Production of Petroleam, Natural Oaa. and Ozokerite.— Section VI.: The Beflnine of Petroleum.— Section VIL: The Shale Oil and Allied Industriee.— Section VIIL: ilie Tranaport, Storage, and Dis- tribution of Petroleum.— Section IX. : The Testing of Crude Petroleum. Petroleum and Shale Oil Products, Ozokerite, and Asphalt.— Section X. : The Uses ox Petroleum and its Products.— Section XI. : Statutory. Municipal, and other Aegulations relating to the Testing, Storage, Transport, and use of Petroleum and its Products.— Appendices. — Bibuooeapht.- Index. "It ii IndlspuUbljr the most oomprehenslTe and oomplato treatise on petroleum, and this statement is true, no matter on what branch of the indasuy a test of its merits is made. ' It is the only book In existence which giyes the oil man a clear and reliable outline of the growth and present-day condition of the entire petroleum world. . . . There is a wonderfully complete collection of plates and lUnstratlons. — fctro^m World. Second Edition, Revieed, With IllustrcUione. Price Se, 6d. net, A HANDBOOK ON PETROLEUM. FOR INSPECTORS UNDER THE PETROLEUM ACTS. And for those enflrasred in the Stopaffe, Tpansport, Distribution, and Industrial Use of Petpoleum and its Ppoauets, and of Calcium Carmde. With suffgestlons on the Constmetlon and Use of Mineral Oil Lamps. By captain J. H. THOMSON, H.M. Chief Inspector of ExploalTes, And sib BOVERTON REDWOOD, Author of " A Treatise on Petroleum." " A Tolnme that will enrich the world's petrt^eam literature, and render a serrloe to the British branch of the industry. . . . Reliable, indispensable, a hrilUant oontrihution."— PttroUum^ In Crown 8to. Fully Illustrated. 28. 6d. net. THE LABORATORY BOOK OF MINERAL OIL TESTINGa By J. A. HICKS, Chemist to Sir Borerton Redwood. •Shonld be on the shelves of every analjrtlcal chemist in practica"— Okesifeai Trad* Jownak In Large Crown 8vo, Cloth. Fully Illustrated 5s. net. O I X^ F XJ S I^: ITS ST7PPLY. OOMFOSITION, AND APPLIOATION. By SIDNEY H. NOBTH, LATI miTOR OF THE "PITROLKUX RIYIIW." Contents.— The Sources of Supply.— Economic Aspect of liquid Fuei— Chemical Composition of Fuel Oils.— Conditions of Combustion in Oil Fuel Fumaoee.- Early Methods and Experiments.— Modem Burners and Methods.— Oil Fuel for Marine Pur- poses.—For Naval Purposes.— On LooomotlTes.— For Metallniglcal and other Purposes. —Appendices. — Ikdsx. " Everyone interested in this important question will welcome Mr. North's excellent text-book."- J^aeure. THB PETROLEUM LAMP: Its Choice and Use. A Guide to the Safe Employ meut of the Paraffin Lamp. By Capt. J. H. Thomson and Sir BovKBTON Redwood. Illustrated, ls.net. "A work which will meet every purpose for which it has been written.**— PefroIaiM. LONDON: CHARLES GRIFFIN A CO., LlMiTED, EXETER STREET. STRAND. 62 0HARLB8 ORIFFIN * CO.'B PUBLIOATlOtTS. (Sriiln 8 SJttallttrgtcal Smts. STANDARD WORKS OF REFERENCE FOR MetaUorglsts, Hine-Ownera, Assayera, Mannfaetnren, and all interested In the development of the Metallurgleal Industries. BDITBD BT Sir W. ROBERTS-AUSTEN, K.C.B.. D.C.L.. F.R.S. /n Lm9j0 8Wp Htmdntm CUik. With lUiutrmHma, nrTBODUOTION to the STUDY of HBTAIiIiirBaT. By the Editor. Fifth Edition. iSs. (See p. 63.) OOIiD (The Metallurgy of). By Thos. ELirke Ross, D.Sc., Assoc R.S.M., F.C.S., Chemist and Assayer of the Royal Mint. Fifth Edition. 21s. (Seep. 63.) IiBAD AND SHiVEB (The MetaUurgy of). By H. F. COLUNS, Assoc. R.S.M., M.Inst M.M. Part I., Lead, 168; Part II., Silver, i6s. (See p. 64.) IB ON (The MetaUurgy of). By T. Turner, A.R.S.M, F.I.C, F.C.S. Third Edition, Revised. (See p. 65.) 8TEBL (The Metallurgy of). By F. W. Harbord, Assoc R.S.M., F.LC, with a Section on Mechanical Treatment by J. W. Hall, A.M. Inst. C.E. Third Edition. 25s. net. (See p. 65.) fvm be PtABsked at Sk^ri InUrvaU, METAIiliTJBaiCAL MACHINEBY : the Application ot Engineering to Metallurgical Problems. By Hbnby Charlbs Jenkins, Wh.Sc., Assoc. R.S.M.» Assoc. M. Inst. C.E., of the Royal College of Science. (See p. 64). COPPER (The Metallurgy of). By Thos. C. Cloud, Assoc. R.S.M. AltLOYS. By Edward T. Law, AssoaR.S.M. *«* Other Volumes in Preparation. LONDON : CHARLES GRIFFIN A CO.. LIMITED. EXETER STREET. STRAND. MBTALLURGWAL WORKS. 63 GBIFFIN'S METAIiLXJBGICAIi SEBIES. Fifth Edition, thoroughly Revised and considerably Enlarged. Large 8to, with numerous Illustrations and Micro-Photographic Plates of different yarietiea of Steel. i8s. An Introduction to the Study of BY Sir W. ROBERTS-AUSTEN, K.C.B., D.C.L., F.R.S., A.R.S.M., Late Chcmiit and Aasayer of the Royal Mint . and Pnrfessor of Metalliugy in the Royal College of Science. Gbnkeal Contsmts.— The Relauon of Metallurgy to Chemistry.— Physical Properties of Metals. — ^Alloys. The Thennal Treatment of Metau. — Fuel and Thermal Measurements. —Materials and Products of Metalluraical Ftt)cesses. — Furnaces. — Means of Supplying Air to Furnaces. — ^Thenao- Chemistry. — laical Metallurgical Processes. — ^The Micro-structure of Metals and Alloys. — Economic Contentions. " No English text-book at all approaches this in the completeness with which the most modem views on the subject are dealt with. Professor Austen's ▼oltima will be invaluable, not only to the student, but also to those whose knowledge of the art is far advanced. "---Olcapii^a/ News, Fifth Edition, Reviaed, Considerably Enlarged, and in part Re-written. With Frontispieoe and numerouB Illustrations. 218. THE METALLURGY OF GOLD. BT T. KIRKE ROSE, D.ScLond., Assoc.R.S.M., Chemiat and Asaayer qf the Royal MinL Qbvbbal Cohtbntb.— The Properties of Gold and lU Alloys.— Chemistry of the Compounds of Gold.— Mode of Ooeorrence and Distribution of Gold.— Shallow Placer Depoaita.- Deep Placer Depoeite. -Quarts Crushine in the Stamp Battery.— Amalgam- ation in the Stamp Battery.— Other Forms of Cnuuiing and AmalgamatlDg Machinery. —Concentration In Gold Mills.— D17 Crushing.— Re-griDding.—Boasting.-Chlorination : The Plattner Process, The Bairei Process, The Yat-Solution Process.- The Cyanide ProcesB.— Chemistry of the Cyanide Process.— B«flning and Parting of Gold Bnllioo. —Assay of Gold Ores.- Assay of Gold Bullion.— Statistics of Gold Production.— Biblio- graphy.—Indkx. ** AooMrurasirsiya praotioju:. tbbatisb on this important subject."— TV Timu. ''The MOST ooMTLsra desertption of the oaLoanvATioir paocias whioh haa yet been pnb- liBhed."-;fta: A Complete and BxhaoBtive Treatise on the hianu^M^are of Lead, with Sections on Smelting and Desilverisation, and Chapters on the Assay and Analysis of the Materials involved. Price i6s. ST7MMART OF CONTBins.— Sampling and AMaying Lead and SUyar.— Pnmerttss and Oompoandi of Lead.— Lead Ores.— Lead Smelting.— Baverberatorlea.— Lead Smelting In Hearths.— The Boasting of Lead Ores.— Blast Fomace Smelting; Principles, PracUoe, and Examples; Products.— Flue Dust, its Composition, Collection and Treatment.— Costs and Losses, Purchase of Ores.— Treatment of Zinc, Lead Sulphides, Desilverlsatton. Softening and Beflning.— The Pattinson Process.— The Parkes Process.— Cnpellation ana Beflning, Ac, Ac "A THOROUOHLT SOUND and useful digest. May with bvsbt ooNnDlMOa be recommended."— if «n Index. " The author has focnssed A largi amount of valuabls xnforicatton into a convenient form. . . . The author has evidently considerable practical experisnoe, and describes the various procmses clearly and well. '—Mining Journal. metallurgical" ifACHINERY : The Application of Engineering to Metallurgloal Probiems. By henry CHARLES JENKINS, Wh. 5c., A880C. R. S if., A 890C. M. Inst. <7. E, LONDON: CHARLES GRIFFIN d CO., LIMITED. EXETER STREET, STRAND MMTALLUROIOAL WORKS, 6$ aBIFFIN'S METAIiLirBaiOAL 8EBIB8. Third Edition, Reviaed. With Nnmeront lUustrationa. Lftrge 8yo. Handsome Cloth. 25b. net. With Additional Chapter on The Electrio Smelting of Steel, THE METALLDRGY OF STEEL By F. W. HARBORD, Assoc.RS.M., F.LC., Oonaulting MetcUlurgiBt and AncUytical Chemist to the Indian Oovernment, Royal Indian Engineering College, Coopers HiU. With 37 PUtes, 280 Illastiations in the Text, and nearly 100 Micro- Sections of Steel, and a Section on THS MECHANICAL TRSATMBNT OF 8TBBL. By J. W. HALL, A.M.Inbt.C.B. Abudoed CoVTKfTS.— The Plftot, Machinerr, Methods and Ohemiatrv of the BeMemer and of the Open Hearth Processes (Aold and Bosio).— The Meo&auical Treatment of Steel oomprislng Mill Practice, Plant and Machinery.— The Inflaenoe of Metalloids, Heat Treatment, Special Steels, Miorostructnre, Testing, and Specifications. ** A work which we renture to commend as an InTsInable compendium of information upon the metallurBT of steel."— /ron and Coal Tradea' Review. The Enaiiutr says, at the conclusion of a review of this book :— " We cannot conclude without earnestly recommending all who maj be interested as makers or users of steel, which praetlcallj means the whole of the engineering profession, to make themselTes acquainted with it as speedilj as possible, and this maj be the more easiij done as the published price, eonsldering the siie of the book, is esttremely moderate." Thied EDiTioir, Revised. Shortly. THE METALLURGY OF IRON. Bt THOMAS TURNER, Assoc.R.S.M., F.I.O., ProfeseoT of Metallurgy in the Unwertity of Birmingham, Iv Labok Syo, Hakdsomb Cloth, With Numebous iLLUSXEATiom (MANY 7BOM PhOTOOBAPHB). Omnral Coa/en/^.—Early History of Iron.— Modem History of Iron.— The A^ of Steal. —Chief Iron Orea.— Preparation of Iron Ores.— The Blast Furnace.- The Air used In the Blaet Furnace.— Beaetions of the Blast Furnace. —The Fuel used In the Blast Furnace.- BlagB and Fnxes of Iron Smelting.— Propertiea of Oast Iron.— Foundry Practioe.— Wrought Iroa— Indirect Production of Wrought iron.— The Pnddiinc Prooesa.— Further Treatment of Wrought Iron. —Corrosion of Iron and Steel. " A MOST TALUABLB siTHMABT of knowledge relating to eTtry method and stage m the maoufaetnre of oast and wrought ixx>& . . . rich in chemical details. . . , SzHAUsnYE and tborouohlt up-to-datk.**— ^u^^^ttn of the AfAtrioan Iron and Steel Auociation, ** This IB A DRUOHTPVL BOOK, giTuig, as it docfi, reliable information on a subject becoming every day more elaborate." — Colliery Ouardian, "A TOORouoHLT ussTiTL BOOK, which brings the snbjeot up to date. Of OREAT VALUE to those engaged in the iron indnatry.** — Minmg Journal, *,* For Professor Tamer's Lectures on Iran- Founding, see page 68. LONDON: CHARLES 8RIFF1N ft CO., LIMITED, EXETER STREET, STRAHa 66 CHARLES QRIFFIN db CO.'S PUBLICATIONS. Tenth Edition. V^ith Tables and lUastrations. Crown 8vo. Cloth, IDS. 6cL A TEXT-BOOK OF ASSAYING: For the use of Students, Mine Managen, Aeeayera, dc By J. J. BERINGER, F.LC, F.C.S., Public Analyst for, and Lecturer to the Mining Association of, CcmwaU. And C. BERINGER, F.C.S., lAte Chief Assayer to the Rio Tinto Copper Company, London, Gbnkkal Comtknts. — Pakt I. -> Introductoky ; MANiPorLAHOir : SarndKof^; Drying ; Calculation of Results— Laboratory-books and Reports. Mbthods : Dry Gravi- metric; Wet Gravimetric— Volumetric Asajrs: Titrometnc, Colorimetxic, Gascnaetiio— Weiglung and Measuring — Resents— F Th€ Bwginttr. "Will oommkud rrsBLF highly in Laboratory Practice. Ite clkabnbss and rmaaiaiov mark the book out as a highly useful ou^."— Mining Journal. LOHDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET. STRAMO. ELECT RO'MBTALLUHOY, ETO. 67 Sbcx)ND Edition, Revised, Enlarged, and in part Re-written. With Additional Sections on Modern Thboribs of Elect roltsis Costs, &c. Price 10s. 6d. A TREATISE ON ELECTRO-METALLURGY: Bmbraoing the Application of Electrolysis to the Plating, Depositing, Smelting, and Refining of varions Metals, and to the Repro- duction of Printwg Sorfaoes and Art- Work, fto. BT WALTER G. MCMILLAN, F.LC, F.O.S., Sieretary to the InttiitUUm of SUetrieal Engineen: UUe Ltetumr II • • 80 W. J. Pbabce, . 80 Knecht and Rawson, . 82 Rawson and Gardner, 82 Cain and Thorpe, 82 H. R. Carter, 83 Setmoub Rothwbll, . 83 W. I. Hannan, . 83 G. H. Hubst, 84 Geo. Dubbb, 84 lONDON : CHARLES GRIFFIN « CO. LIMITED. EXETER STREET. STRAND- 70 CHARLES GRIFFIN d> CO.'S PUBLICATIONS. Third Edition, Revised, Enlarged, and Re-issaed. Price 6s. net. A SHORT MANUAL OF INORGANIC CHEMISTRY, By A. DUPRE, Ph.D., F.R.S., And WILSON HAKE, Ph.D., F.LO., F.C.S., Of the Westminater Hcwpital Medical School "Am bzamflx or thb advamtagbs of thb Systematic THXATmirr of a Sdosoe over the fragmentary style so generally followed. Bv a lomg way tkb bbst of the snail Manuals for Stodents.**— ^Mo/yf/. In Handsome Cloth. With nearly 50 Illustrations. 38. 6d. net. THE ELEMEHTS OF CHEMICAL EHGIHEERIHG. By J. QROSSMANN, M.A., Ph.D.. F.I.C. WITH A PREFAOB BT Sib WILLIAM RAMSAY, K.C.B., F.R.S. OOHTEins.— The Beaker and its Technical EqaiTaleDt8.—DifltOUng Flasks, Llebig'f CtondenserB.— IfractloDatlng Tubes and their Technical Eqalvalents.— The Atr-Bath and its Technical BqulTalents.— The Blowpioe and Crucible and their Technical BqalYalenta. —The Steam Boiler and other Sources of Power.— General Bemarks on the AppUcatioa d Heat in Chemical Engineering.— The Funnel and its Technical Bquivalenta.— The Mortar and its Technical Equivalents.— Measuring Instruments and their Technical Bquivalents.- Materials Used in Chemical Engineering and their Mode of Applicatlou.— Technical Research and the Designing of Plant.— Conclusion.— Chemicals and Materials. — INDHX. "Excellent. . . Every student of chemistry attending a technical coarse should obtain a copy. '^Ohemical Newt. LABOBATOBT HANDBOOKS BT A HUMBOLDT SEXTONi Profeesor of Metallargy in the Qlaagow and West of Sootland Technloal Ck>lleffs. OUTLINES OF QUANTITATIVE ANALYSIS. FOR THB USS OF 8TUDSNTS, With nioBtrationB. FitTH Edition. Grown 8vo, Cloth, Si. ** A ooxpAOT LABOBATOBT ouiDB for bsginners was wantsd, and the wsnt has been WBLL sufflibd. ... A good and nsefiil book."— £an«e<. OUTLINES OF QUALITATIVE ANALYSIS. FOR THB USB OF 3TUDBNTS. With niostrations. Fourth Edition, Revised. Crown 8vo, Cloth, Sa. 6d. '* Ths work of a thoroughly prsotioal chemist"— BrtittA Medical JaumaL « OompQed with grsat cars, and will supply a want."— JottmoJ of RdiuaHan. ELEMENTARY METALLURGY: Inolnding the Author's Praotioal Laboratory Conrae. [See II. 66. CORDON : GHARLE8 BRIFFIN & CO.. LIMITED, EXETER STREET, STRANOl. OHEUiSTRT AND TKCHNOLOOT. 71 "Th« aufebon hAr« svociibbo befoad all flzpaoUtloiu. «ad h».w produo^d » work wld«h •hoold siTe f aisR rowia to the Bngloeer and BCaoafkcCnrar/'^TV 3* Olive Oil.— Water Analysis.— Appendix : Adulteration Acts, &o. 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IX.— Inorganic Poisons. Appmdix : Treatment, by Antidotes or otherwise, of Cases of Poisoning. '* UndoaMedly vhs moh oohplk ■ woax on Tozioolocy in cor langnaiwi "—ITU A%m\m^ /on f *• Third IMMdi). ^^ ** At a nucTiOAL eoxni, we know so smn work."— 3 k« Lnmea fen tkt Third EdUitni. *•* In the Taian S»inos. Xnlaiied and partly Be-wrltten, Niw AjrALnioAi ManoM have beoB introdnoed. and the Oadatieio Aualoids, or PvoHAXiiii, bodlei playtar eo graat a pact In lywd-polKmlnff and in the Manifeitatlone of Dtieeia. hare reoeired ipeeial atf ttoa. lONDOh : CHARLES 8RIFFIN i CO.. LIMITED. EXETER STREET, STRAND 0HSM18TRY AND nSVHUOLOGT. 73 With NumeroQs Tables, and 22 lUustratioiu. i6s. DAIRY CHEMISTRY FOB DAIBT MANAGERS, CHEMISTS, AND ANALYSTS A Practical Handbook for Dairy Chemists and others having Control of Dairies. By H. droop RICHMOND, F.I.C, CHEMIST TO THB AYLESBURY DAIRY COUPAKY. Contents.— I. Introductory. — The Constituents of Milk. II. The Analysis of Milk- III. 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" Without doubt the best contribudon to the literature of its subject that has ever been written."— ^V# LancA, Crown 8vo, Handsome Cloth. With Diagrams. 7s. 6d. net. [Companion Volume to ** FERMENTS," by the same Author,'^ TOXINES AND ANTITOXINES. By OARL OPPENHEIMER, Ph.D., M.D., Of the Fh]rsioIogicaI Institute at Erlangen. Translated from the Germak by 0. AINSWORTH MITCHELL, B.A., F.I.C., F.C.S. With Kotes, and Additions by the Author, since the publication of the Oennan Xdittoo. *' For wealth of detail, we have no small work on Toxines which equals the one under review."— Jfcdico/ Tinie», lONOON : CHARLES GRIFFIN « CO.. LIMITED, EXETER STREET. STRAND Oa&MiSTRY AND TMOHNOLOOY. 75 In Grown 8vo, Handsome Cloth. Price 7b. 6d. net. r E R M E N TS A XT D rr SE E X IS JBLCXXOXTB. A Text-book on the Chemistry and Phyetoa of Fermentative Ghangee, By carl OPPENHEIMER, Ph.D., M.D., Of the Physiological Institute at Erlangen. Tbanslated fhoh ths Oebman bt C. AINSWORTH MITCHELL, B.A., F.LC, P.CS. ABRIDOBD CONTEHTS.— Introdaction.~DeA]iltioii.— Chemicftl Katnre of Feraaenta.— Influence of External Factors.— Mode of Action.— Physiological Action.— Secretion.— Importance of Ferments to Vital Action.— Proteolytic Ferments.— Trypsin.— Bacteriolytic ana Hnmolytlc Ferments.— Vegetable Ferments.— Coagulating Ferments.— Saccharl^nos Ferments. — Diastases. — Polysaccharides. — Enzymes. — Ferments which decompoee Olncosldes.— Hydrolytic Ferments.— Lactic Add Fermentation.— Alcoholic Fermenta- Uon.— Biology of Alcoholic Fermentation.— Oxydases.— Oxidising Fermentation.— Biblt* Qgrapb7>— INPIX. '^ Booh a veritable m^atrnm in parvo baa Dever yet appeared. "^Arvirert* /ourmai. Third Editiok. In Handsome Cloth. Fully Illustrated. 2l8. net. PRINCIPLES AND PRACTICE OF BREWING. FOR THE USE OF STUDENTS AND PRACTICAL MEN. By WALTER J. SYKES. Revised by ARTHUR R. LING, P.LC, P.C.S., Editor of the Journal of the Institute of Brewing. 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In Two VoIufntSy each complete in iiselj, PHYSICO-CHEMICAL TABLES FOR THE USE OF ANALYSTS, PHYSICISTS, CHEMICAL MANUFACTURERS AND SCIENTIFIC CHEMISTS. Voinme I. — Chemical Engineering, Physical Chemistry. Vohime II. — Chemical Physics, Pnre and Analytical Chemistry. [Shortly, By JOHN CASTELl^EVANS, F.I.C., F.C.S., Lecturer on Inorganic Chemistry and Metallurgy at the Finsbury Technical College. The Tables may almost claim to be exhaustive^ and embody and collate all the most recent^ data established by experimentalists at home and abroaid. The volumes will be found invaluable to all engaged in research aad experimental investigation in Chemistry and Physics. The Work comprehends as Cur m possible all tULU and Tablbs required by the Analyst, Brewer, Distiller, Acid- and Alkali-Manu&cturer, &c., &c. ; and slUo the prin. cipal datm in Tmbsmo-Chimistrt, Elbctso-Chsmistav, and the various branches of Ckbmical Physics. Every possible care has been taken to ensure perfect accuracy, and to include the results of the most recent investigations. Second Edition. In Large %vo. Handwme Cloth. Bea%UifiMy nitutrated. With Plates and Figure* in the Text. Road Making and Maintenance: A PBACTIOAIi TBEATIBB FOB ENGIHBEBS, STTBVEYOBSy AND OTHEBS. With an Hibtobical Sketch of Anoixnt and Modbbn Practici. By THOS. AITKEN, AssocM.Ihst.O.E., Member of the Association of Uaoietp*! and Oonnty Sngtnesn; Member of the Sanitary Inst ; Surveyor to the Oonnty Coonell of Fit: Onptf Dlviaion. WITH Nuaeaoas platss, oiAeRAus, amo lauaTRATiONs. Contents.— Historical Sketch.— ReaiBtance of Traction.— Laying oat New Roads. — Barthworks, Drainage, and Retaining Walla. — Koad Materials, or Metal. — Quarrying. — Stone Breaking and Haulase. — Road» Rolling and Scarifying. — The Construction of New, and the Iwntenanoe of existing Roads. — Carriage Ways and Foot Ways. "The Literary style is izaium. . . . 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CoHTSNTS. — HistoricaL — Glub. — Gelatine. — Size and Isinglass.— Treatment of Efflu- ents produced in Glue and Gelatine Making.— Liquid and other Glues, Cements, &c.— Uses of Glue and Gelatine. — Residual Products.— Analysis of Raw and Finished Producu.— Appsmdix. — Indkx . '* A sufficient account of modem methods of working, chiefly from a pracdcal standpoint. A book ... of real value.*' — Chemical Neufs, At Prrss. In Large 8vo. Handsome Cloth. Fully Illustrated. THE ANALYSIS OP MATERIALS USED IN GDKEl XiESJiLGDHSXt I NT D XX S T IT Y^. Bt S. R. TROTMAN, M.A., F.I.C, Public Analyst for the City of Nottingham, Member of the International Association of Leather Trades* Chemists. Synopsis ow Contents.— Standard Solutions.— Adds, Alkalies, &c.— Water.— Depilation a nd Deliming.— Fleshings, &c.— Glue.— Spent Liquors.— Mineral and Vegetable Tanning Agents. — Oils. — Soaps.— Varnishes. — Skin. — Leather. — Dyestuffs — Degreasing Agents. — Effluents.- Glcssary. — Index. In Medium 8vo, Handsome Cloth. Fully Illustrated. 12s. 6d. net. PAPER TECHNOLOGY: AN BLBMBNTARY MANUAL ON THE MANUFACTURE, PHYSICAL QUALITIES. AND CHEMICAL CONSTITUENTS OF PAPER AND OF PAPERMABING FIBRES. With Selected Tables for Stationers, Publishers, and Others. Bv R. W. SINDALL, F.C.S. CoNTBNTS.->-Introduction. — Technical Difficulties relating to Paper.— Rag Papers.— Esparto, Straw, Nous on Beating.— Wood Pulp.— Wood Pulp Papers.— Packing Papers — "Art" Papers.— The Physical Qualities of Paper.— The Chemicsd Constituents of Paper. — The Microsoope.— Fibrous Materials used in Paper • making — Analysis of a Sheet of Paper.— The C.B S. Uniu. -Cellulose and its DerivatiTes.— History, Chronology, and Statistics.— Dictionary of 0»n*kyl Terms.— Glossary. — City and Guilds Questions.— Index. '* Exceedingly instructive and particularly useful." — Paper Maktrs Monthly Journal, In Laige 8vo. Handsome Cloth. With Plates and Illustrations. 7s. 6d. net. THE MANUFACTURE OP INK. A Handbook of the Production and Propertiee of Printing, Writing, and Copying Inka, \ By C A. MITCHELL, B.A., F.I.C, F.C.S., & T. C HEPWORTH. I "Thoroughly well arranged . . . and of a genuinely practical order.'*—^nVf<^/'rr>ii!rr. LONDON : CHARLES SRIFFIN ft CO.. LIMITED, EXETER STREET, STRANa 82 0HARLE8 ORIFFIN A OO.'S PUBLIC ATIOIS 8. SKC027D Edition, Thoroughly HevUed Tkroughout. In Two Largt Vohimes, Handsome Cloth. A MANUAL OP DYEING s FOR THE V$i Of PRACTICAL DYERS, HIAnVEACTURERR, STUDENTS, AND ALL INTERESTED IN THE ART OF DYEING. E. KNECHT. Ph.D., F.LC. ^^ CHR RAWSON, F.I.C.. F.C.S., EmA of th« OlMiniitrT And Dyeing D«p«tmMit of L*to HomI of tho Cb«ml«tr)r and Djrolac Dap^tBoft Om TtohnlMl Bohoel, JUnefaMtori Bdltor of "Tha of tiio TMhalml Oolkm, Bndfotd : MomUr JouimI of tlio Boolotj of Dyvn aod OolonrUti ; " Ooonoil of the BodotF of Dyan and OoIovxIslfU And RICHARD LOEWENTHAL, Ph.D. Gbnbral Contkkts. — Chemical Technology of the Textile Fabrice— Water -^-Waahing and Bleaching -- Adds, Alkalies, Mordants -- Natural Oolooring Matters— Artificial Organic Colonring Matters— Mineral Colours —Machinery nsed in Dyeing — Tinctorial Properaes of Colouring Matters — Analysis and Valuation of Materials used in Dyeing, Ac, Ac '* This anthorltatlYe and ezhMStlire work ... the mobt ookplbti ivs bave yet on the mib|eot'*— A»rlouring Matters in the Victoria TJniTerslty of Manchester. Part I. Theoretical. Part II. Practical. Pan III. Analytical. " We have no hesitation in describing this treatise as one of the most Taluable books that has appeared. . . . Will erlve an impetus to the study of Organic Chemist generally.'*— CAemtcoil 2 rade Joarnal. Companion Volume to Knecht <£; Raioson'a ** Dyeing." In Large 8vo. Handsome Cloth, Library Style. 16s. net. A DICTIONARY OF DYES, MORDANTS, & OTHER COMPOUNDS USED IN DYEING AND CAUGO PRINTING. with Formulm, Propsrtles, and Apptiaattons of ttis various substaness deserlbsd, and concise directions for their Commercial Valuation, and for the Detection of Adulterants. By CHRISTOPHER RAWSON, I^.I.C, P.C.S., Consulting Chemist to the Behar Indigo Planters' ABSoclation ; Co- Author of " A Manual of Dyeing:" WALTER M. GARDNER, F.C.S., Head of the Department of Cheulttry and Dyeing, Bradford Mnaldpal TMbaieal Oollege : Editor of the " Joom. 8oc Dyers and Colouristo : " And W. F. LAYOOCK, Ph.D., F.O.S., Analytical and Oonsnltlng Cheinlst *' Turn to the hook At one may on any aubjeot, or any tnbstAnoe in Mnncotion with the trade, and a referenoe is sure to be found. The anthors haye apparently left nothing out." ^Textile Mercury. !!■ I I I - ■ ■ M III! ■ IIM ■ I ■■ I I I ^^—^^^^^ LONDON : CHARLES GRIFFIN A CO.. LIMITED. EXETER STREET, STRANIk THS TEXTILE INDUSTRIES, 83 Large 8vo. Profusely Illustrated with Plates and Figures in the Text. I69. net. THE SPINNING AND TWISTING OF LONG VEGETABLE FIBRES (FLAX, HEMP, JUTE, TOW. A RAMIE). A Pnetieai Manual of tli9 most Modern iiethoda at applhd to the Hackling, Carding, Preparing, Spinning, and Twisting of the Long ¥ eg stable Fibres of Commerce. Bt HERBERT R. GARTER, Belfast and Lille. Oknbral CoNTiRtB.— Long Vesetable Fibres of Commerce.— Siae and Growth of the Spinning Indostrr.-^Baw Fibre Markets.— Pnrchasing Saw HaterlaL—Storing and Preliminary Operations.— Hackling.— Sorting.— Preparing.— Tow Carding and Mixing.— TowCombing.—OlUSptnnlBg.— The Koviug Frame. —Dry and Demi-sec Spinning.— Wet Spinning.— Spinning waste.- Yam Reeling.— Manufacture of Threads, Twines, and Cords.- &ope Making.— The Mechanical D^;>artment.-'Modem Mill Construction.- Steam and water Power.— Power Transmission. " Meets the requirements of the Mill Manager or Adranced Student in a manner perhaps more than satisfactory. . . . We most highly commend the work ss repre- senting up-to-date practice."— J^ature. In Large Svo, ffandUtnne Cioth, with Numerous Jllustrations, 9s. net, TEXTILE FIBRES OF COMMERCE. A HANDBOOK OF The 6ooiirrenoe, Distributioiiy Preparation, and Industrial XTses of the Animal, Vegetable, and Mineral Froduots used in Spinning and Weaving. By WILLIAM I. HANNAN, Lecturer on Botany at the Ashton Municipal Technical School, Lecturer on Oottoii Spinning at the Chorley Science and Art School, Ac. With Numerous Photo EngravlngB fh>m Nature. ** UssrcL IiardB.— The Steam Style.— Ck>loani Produced Directly on the Fibre.— Djred Styles.— Padding Style.— Resiet and Diaoharge Styles.- The Printing of Compound ColourinsB, ftc— The Printing of Woollen Oooda.- The Printing of Silk GkMdB.— Practical Recipes for Printing.— Useful Tables.— Patterns. " Bt var thx uwaa and voer rsAonoAL book on tbxtilb ranrmio which has yst been brought out, and will long remain the standard work on the snbjeot It is essentially practical in character.**— 2V7(jtAa%, and Printing Dvpirtmmit at the Aecrincton and Baeap Technical Bohoola ; Chemist and Ooloorlat at the IrweU Print Worka. AssiSTSD BT WILLIAM TURNBULL (of TarabuU 4( Stockdale, Limited). With lUuBtratioxu and upwards of One Hundred Dyed and Printed Pattema designed speoially to show various Stages of the Prooeosos deaoribed. GENERAL CONTENTS.— Cottok, CompoBition of; Blxachiko, New Processes ; Printdvo, Hand-Block ; Ilat-Press Work ; Machine Printing— MoBDANTB— Sttlxs OF Calico-Primtino : The Dyed or Madder S^le, Reinst Padded S^le, Discharge and Extract Style, doomed or Raisea Colours. Insoluble Colours, &c — Thickeners — Natural Organic Colouring Matters —Tannin Matters— Oils, Soaps, Solvents— Organic Adds— Salts— Mineral Colours — Coal Tar Colours — I^eing — Water, Softening of —Theory of Croloura — Weights and Measures, &c. '* When a biadt way oat of a dUBcoIty Is wanted. It it is books lies this that It la foond.'— Itelflf Jieeordcr. "Mr. Dusek's wobk will be found most vsbpul . . . The Information sItcb is of exsat T4L0B. . . . The Recipes are TBOBonoBLT paacnoAk"-'T«a(il< Afami/lMiiirw. Second Edition. Revised and Enlarged. With Numerous Illustrations. 4s. 6d. GARMENT DYEING AND CLEANING. A Practical Book for Practical Hen. Bv GEORGE H. HURST, F.C.S., Member of the Society of Chemical Industry. GsNBRAL CONTRNTS.— Technology of the Tertile Fibres — Garment Cleaning —Dyeing of Textile Fabrics— Bleaching— Finishing of Dyed and Cleaned Fabrics- Scouring and Dyeing of Skin Rugs and Mats — Cleaning and Dyeing of Feathers- Glove Qeaning and Dyeing — Straw Bleaching and Dyeing — Glossary of Drugs and Chemicals— Useful Tables. *' An up-TO-DATB hand book has long been wanted, and Mr. Hunt has done nothing more complete than this. An important work, the more so that several of the branches of the cnit here treated upon are almost entirely without English Manuals for the guidance of workers. The price brings it within the reaoi of all."— J>/rr mttd CaUe^-PrmUr. ** Mr. Hunt's wonc dbcidbdly fills a wamt . . . ought to be in the hands ol €VBiKY GARMENT DYER and deaner in the Kingdom**— TVxIfiSr Miratry, LONDON : CHARLES QRIFFIN & CO.. LIMITED, EXETER STREET. STRAND. INTRODUCTORY SCIENCE SERIES. 85 " Boyi OOVLD HOT HAYB ▲ MOBl ALLUBIHO IBTBODUOTIOir tO MleDtlflo panoltl than thme oharmiDg^looUxig ▼olnmet."— Letter to the Publlihevt from the Head- mMter of one of oor great Poblic Schooli. Handaome Cloth, 78. 6d. Qilt, for Preaentation, 8fl. 6d. OPEll-AIli STUDIES qi BOTAjlY: SKETCHES OF BSITISH WILD FLOWEBS IK THEIB HOMES. Bt R. LLOYD PRAEQER, B.A., M.R.LA. Illustrated by Drawings fl*om Nature by S. Rosamond Praeger, and Photographs by R. Welch. QsMSBili CoNnHTB. — A Dduiy-Starred Paatnre — Under the Hawthoma —By the River — Along the Shingle— A Fragrant Hedgerow— A Connemara Bog — Where the Samphire nrowa — A Flowery Meadow — Among the Ck>m (a Study in Weeda)— In the Home of the Alpinea— A Oity Rnbbiah-Heap— Qlosaary. "A FRKB Ain> BTOiVLATiHa book . . . ihoiUd take a high plaoe . . . The ninetratfcme an drawn with much ikill."— PAe Times. " BBAunvuLLT ILLUSTBATID. . . . One of the xon AOOUBAn as well ae OfTnuuxiHO booki of the kind we ha^e Men."— ^tAmAuvk "Hedolent with the loent of woodland and meadow."— 2!ft6 SUmdatrd, \¥ith 12 Full-Page llluBtratlona from Photoarapha, Cloth. Second Edition, Reviaed. 8a, od, OPE]l-AUl STUDIES I]l GEOItOGY: An Introduetion to Geolc^ry Out-of-doors. By GRENVILLE A. J. COLE, P.G.S., M.R.LA., Frofenor of Gaology in the Boyal College of Sdenoe for Ireland, and Bzaminer In the UnlTeni^ of London. Gkkbbal Gomtkmts.— The Materiala of the Earth— A Mountain Hollow —Down the Valley — Along the Shore — ^Aoroas the Plains — ^Dead Voloanoea —A Granite Highland— The Annak of the Earth— The Surrey Hilla— The Kolda of the Moontaina. *'The rAaonrAnvo *Onai-Aia Srunxia' of Paor Ooui glTe the rabjeot a glow or AimiATioy . . . oaanot fall to aroiue keen Intereet in geology.**— Itaofo^tea/ lioffaxmt. ** A OHABimio aooK, beaatifnlly illaatrated.** -Athenimm. Beautifully llluatrated. With a Frontlapieoe in Coloura, and Numeroua Specially Drawn Platea by Charlea Whymper. 7a, 6d. OPEjl-AIIt STUDIES I]l 6I1U>., Societies occupy- ing thoBuelTes with aeTeral Branches of Science, or with Science and literature jointly. I a. Ifathematics and Physics. 1 3. Chemistry and Fhotogtaphy. 1 4. Gedogy, Geography, and MiscralMy. I $. Bicdogy, including Microscopy and An- thropology. 9 6. Eoonomic Saenoe and Statistics. 9 7. Mechanical Science, Engineering, Architectnre* fi 8. Naval and MflitflCT Saenoe. i 9. Agriculture and Horticulture. Sxo. Law. ( xz. literature. |xa. Psychology. 9x3. A»rhwol